USB: storage: ene_ub6250: fix compile warnings

Fix the following compile warning:

| drivers/usb/storage/ene_ub6250.c: In function ‘ms_scsi_write’:
| drivers/usb/storage/ene_ub6250.c:1728:6: warning: ‘result’ may \
|	be used uninitialized in this function [-Wuninitialized]
| drivers/usb/storage/ene_ub6250.c:1795:77: warning: ‘offset’ may \
|	be used uninitialized in this function [-Wuninitialized]

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>