msm: vidc: Use mutex_trylock for core lock in trigger ssr

Userspace thread can acquire debugfs_srcu lock while waiting
for core lock to trigger ssr. Core lock can be acquired by
worker thread while unregistering bus client as a result of
sys error. Unregistering bus client involves removing debugfs
node which gets blocked on debugfs_srcu lock, leading to deadlock.

Use mutex_trylock for core lock in trigger ssr, to avoid deadlock.

Change-Id: Ib77117be2c51aa49508b0dafcbbd99fd5cf04bf2
Signed-off-by: Surajit Podder <spodder@codeaurora.org>