fs/yaffs2/yaffs_guts.c: Fix GCC 4.6 compile warning (and bug)

fs/yaffs2/yaffs_guts.c: Fix GCC 4.6 compile warning (and bug)

Fix:
yaffs_guts.c: In function 'yaffs_GarbageCollectBlock':
yaffs_guts.c:2761:6: warning: variable 'retVal' set but not used
[-Wunused-but-set-variable]

Here GCC actually detected a bug.  The code was always returning OK
instead of the previously set retrun code.  Fix that.

Signed-off-by: Wolfgang Denk <[email protected]>
Cc: William Juul <[email protected]>
Cc: Scott Wood <[email protected]>
Acked-by: William Juul <[email protected]>