drivers: msm-poweroff: Flush all caches during reset

During reset path flush all the caches so that the kernel logs and data
structures are available as part of the ddr dump for debugging.

Change-Id: Iec2bc0de9c9b90e2f42fe0c11e636d86cc7eeac1
Signed-off-by: Channagoud Kadabi <ckadabi@codeaurora.org>