msm: ipa: Fix considering prefetch buf size when mapping

IPA HW tries to prefetch 128 Bytes of additional memory when
dealing with filter/routing tables. This can result in overflowing
of memory if we map only the required size. Make changes to
consider prefetch memory when allocating routing/filter tables.

Change-Id: Id72e4df285a4683dddebb18d98bb9c4dd9667eeb
Signed-off-by: Chaitanya Pratapa <cpratapa@codeaurora.org>