mmu-hash*: Reduce use of access_type

In ppc env->access_type is updated by e.g. integer load/stores with
ACCESS_INT floating point load/stores with ACCESS_FLOAT and so forth.  In
hash mmu fault paths it can also b set to ACCESS_CODE for instruction
fetch accesses.

But the only place which uses anything more of the access_type than
whether it is instruction fetch or data access is the direct store segment
handling.  Instruction versus data access can be more simply determined
from the rw value passed down from the top.

This changes the code to use rw in preference to checking access_type.
For the 32-bit case there is a small amount of code (for direct store
segments) that still needs the full access type.  Instead of passing it
all the way down the stack, we retrieve it from the env structure, which
is where it came anyway, before this patch.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>
