msm: ipa: add support for modem SSR

As part of modem Sub System Restart, ipa driver needs to perform
cleanup before the modem goes down and reinitialization after the
modem goes back up.

CRs-Fixed: 675048
Change-Id: I39b156f2060b47c3bdbe9236a5129055b2d854dd
Signed-off-by: Sivan Reinstein <sivanr@codeaurora.org>