Fix snprintf in CameraDriver.cpp

When a camera effect was removed from the supported efect modes, which
was built using snprinf, a %s corresponding to that effect was left in
the snprintf format, causing a SIGSEGV.
Fixed the snprintf format.

Change-Id: If1be1658b2f5ed449e6ac1ce09cc70863b570071
Signed-off-by: Robert Chiras <robert.chiras@intel.com>