cciss: fix compile issue

drivers/block/cciss.c: In function ‘cciss_send_reset’:
drivers/block/cciss.c:2515:2: error: implicit declaration of function ‘fill_cmd’
drivers/block/cciss.c: At top level:
drivers/block/cciss.c:2531:12: error: conflicting types for ‘fill_cmd’
drivers/block/cciss.c:2534:1: note: an argument type that has a default promotion can’t match an empty parameter name list declaration
drivers/block/cciss.c:2515:18: note: previous implicit declaration of ‘fill_cmd’ was here
make[1]: *** [drivers/block/cciss.o] Error 1
make: *** [drivers/block/cciss.o] Error 2

Move fill_cmd() to above where it is first used.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>