Fix use of uninitialized value

This fixes multiple warnings that look like:

packages/apps/LegacyCamera/jni/feature_mos_jni.cpp:371:8: warning:
variable 'ret_code' is used uninitialized whenever '&&' condition is
false

(We only init ret_code in the if block, not the else. It's later
unconditionally assigned to gTRS[10]).

Bug: None
Test: mma. Warning disappeared.
Change-Id: I5993dafa68ca64fd5e467789be0ca747f0805426