Remove the useless variable 'partial' storing the actual length
transferred. Nothing was done with it, so simply get rid of it
as usb_stor_bulk_transfer_buf can handle having NULL instead.
This also fixes the following sparse issues (-Wtypesign):
drivers/usb/storage/karma.c:122:51: warning: incorrect type in argument
5 (different signedness)
drivers/usb/storage/karma.c:122:51: expected unsigned int *act_len
drivers/usb/storage/karma.c:122:51: got int *<noident>
drivers/usb/storage/karma.c:127:52: warning: incorrect type in argument
5 (different signedness)
drivers/usb/storage/karma.c:127:52: expected unsigned int *act_len
drivers/usb/storage/karma.c:127:52: got int *<noident>