msm: modem-ssr-8974: Add support for phase 3 modem restart

Add support to restart just the modem when it encounters
a fatal error. This includes calling PIL to shutdown and
boot the modem up, as well as adding support to allow
userspace to collect the modem ramdump.

Change-Id: I0cd3a662e555a7a1c6104f714ae133b382414500
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>