API: indexing DatetimeIndex with date object
- [x] I have checked that this issue has not already been reported.

- [x] I have confirmed this bug exists on the latest version of pandas.

- [ ] (optional) I have confirmed this bug exists on the master branch of pandas.

---

**Note**: Please read [this guide](https://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports) detailing how to provide the necessary information for us to reproduce your bug.

#### Code Sample, a copy-pastable example
down load this file 
[bug.xlsx](https://github.com/pandas-dev/pandas/files/5105345/bug.xlsx)

or create an excel file with the follwoing:

col1 | 8/21/2020  12:00:00 AM
-- | --
value | 10.1



then run the following code

```python
    import pandas as pd
    import datetime as dt

    df = pd.read_excel("bug.xlsx", index_col=0)
    toto = df[dt.date(2020, 8, 21)]

```

#### Problem description
I have this error on 1.1.0 and 1.1.1:
```python
  File "C:/Users/snoof/PycharmProjects/palms_db_script/palms_db.py", line 58, in <module>
    toto = df[dt.date(2020, 8, 21)]
  File "C:\Users\snoof\PycharmProjects\palms_db_script\venv\lib\site-packages\pandas\core\frame.py", line 2899, in __getitem__
    indexer = self.columns.get_loc(key)
  File "C:\Users\snoof\PycharmProjects\palms_db_script\venv\lib\site-packages\pandas\core\indexes\datetimes.py", line 622, in get_loc
    raise KeyError(key)
KeyError: datetime.date(2020, 8, 21)
```

#### Expected Output

no error, with pandas 1.0.5, it finds the element.

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

<details>

INSTALLED VERSIONS
------------------
commit           : f2ca0a2665b2d169c97de87b8e778dbed86aea07
python           : 3.7.3.final.0
python-bits      : 64
OS               : Windows
OS-release       : 10
Version          : 10.0.19041
machine          : AMD64
processor        : Intel64 Family 6 Model 94 Stepping 3, GenuineIntel
byteorder        : little
LC_ALL           : None
LANG             : None
LOCALE           : None.None
pandas           : 1.1.1
numpy            : 1.19.1
pytz             : 2020.1
dateutil         : 2.8.1
pip              : 20.1.1
setuptools       : 49.1.0
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
fsspec           : None
fastparquet      : None
gcsfs            : None
matplotlib       : None
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
pyxlsb           : None
s3fs             : None
scipy            : None
sqlalchemy       : None
tables           : None
tabulate         : None
xarray           : None
xlrd             : 1.2.0
xlwt             : None
numba            : Non


</details>
