msm: ipa: add 64-bit support for IPA

This change has 64-bit compilation fixes and other
related cleanup.

On targets with IPA HW that mainline code applies to, A2 HW block no
longer exists. This makes a bunch of code (like a2_service.c,
ipa_bridge.c) obsolete. Also, teth_bridge.c is significantly different
because a new IPA driver running on Q6 subsumes most of the
functionality. We need an atomic change to ensure tethering
functionality does not break.

Change-Id: I279e6605dd30b0b8fc03808b69931c749c461914
Signed-off-by: Ravi Gummadidala <rgummadi@codeaurora.org>