Unable to change normalize property of objects from to_offset()
#### Code Sample, a copy-pastable example if possible

```python
from datetime import date

from pandas.tseries.frequencies import to_offset
from pandas.tseries.offsets import DateOffset


dt = date.today()
offset = to_offset("52W")
print(f"type: {type(offset)}\ndict: {offset.__dict__}")
print(f"{dt} -> {dt + offset}")

try:
    offset.normalize = True
except AttributeError as ex:
    print(f"\n{ex}")

offset = DateOffset(normalize=True, **offset.kwds)
print(f"\ntype: {type(offset)}\ndict: {offset.__dict__}")
print(f"{dt} -> {dt + offset}")
```

Yields
```
type: <class 'pandas.tseries.offsets.Week'>
dict: {'n': 52, 'normalize': False, '_cache': {}, 'weekday': 6}
2019-08-03 -> 2020-07-26 00:00:00

DateOffset objects are immutable.

type: <class 'pandas.tseries.offsets.DateOffset'>
dict: {'n': 1, 'normalize': True, '_cache': {}, '_offset': relativedelta(weekday=SU), '_use_relativedelta': True, 'weekday': 6}
2019-08-03 -> 2019-08-04 00:00:00
```
#### Problem description

Since Pandas `0.24` the `DateOffset` objects are immutable. Previously it was possible to change the `normalize` property after receiving an object from `to_offset()`, but now there doesn't seem to be any mechanism for doing this. While it seems possible to create a new instance of `DateOffset` with `normalize = True`, the type of the object changes and doesn't work correctly.

What is the best way of getting an object from `to_offset()` with `normalize` set to `True`? From an end-user perspective, the best solution would probably be to add a normalize attribute to the function, like so:

```python
def to_offset(freq, normalize=False):
```

#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.3.final.0
python-bits      : 64
OS               : Darwin
OS-release       : 18.6.0
machine          : x86_64
processor        : i386
byteorder        : little
LC_ALL           : en_US.UTF-8
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 0.25.0
numpy            : 1.17.0
pytz             : 2019.2
dateutil         : 2.8.0
pip              : 19.2.1
setuptools       : 41.0.1
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : None
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : None
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
s3fs             : None
scipy            : None
sqlalchemy       : None
tables           : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None

</details>
