wil6210: support aggregation max window size 64

FW can support BACK window size 64 for performance improvements.
A new FW capability is added for notifying the host on the increased
max BACK win size support.
Defining WIL_MAX_AGG_WSIZE_64 and WIL_MAX_AMPDU_SIZE_128 to be used
in this case.

Change-Id: I174c20a78cb2cb7987c782698fb6cee02d10a09b
Signed-off-by: Maya Erez <merez@codeaurora.org>