msm: camera: common: Enable debugfs compile check.

Guards debugfs features in camera driver to only be compiled when
CONFIG_DEBUG_FS is enabled.

CRs-Fixed: 2717236
Change-Id: I0de77741301d259cbec64e8a2e27830981b2b69d
Signed-off-by: Karthik Jayakumar <kjayakum@codeaurora.org>