memstick: suppress uninitialized-var warning

drivers/memstick/host/tifm_ms.c: In function 'tifm_ms_data_event':
drivers/memstick/host/tifm_ms.c:185: warning: 'p_off' may be used uninitialized in this function

Cc: Alex Dubov <oakad@yahoo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>