msm: vidc: Suppress false error messages

When parsing the device tree the driver emits false error messages when
optional properties are not found.  This commit gracefully handles the
absence of optional properties.

Change-Id: I34c58513e8fa62e6862b8c630814930554ff18fb
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>