msm: camera: avoid race condition while configuring ping pong buffer

Issue) Deadlock occur when cfg_ping_pong function called from
two different cores, since one core is trying to acquire the
lock for vfe1 which is hold by anoter core and another core
is trying to acquire the vfe0 lock hold by actual core, which
leads deadlock.
Resolution) To avoid this will make a common lock for both
vfe.

Change-Id: I2d2480154f1c9e00910620e1a749bb49b5eca955
Signed-off-by: Ramesh V <ramev@codeaurora.org>