msm: restart: flush the cache before restart

Currently during panic case, the ramdump does not have the last part
of dmesg because of cache not getting flushed. Hence flush the cache
during restart.

Change-Id: I2e6971e8f67a29a950e8c3a68fbf340a4c222ee8
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>