[media] rainshadow-cec: avoid -Wmaybe-uninitialized warning

The barrier implied by spin_unlock() in rain_irq_work_handler makes it hard
for gcc to figure out the state of the variables, leading to a false-positive
warning:

drivers/media/usb/rainshadow-cec/rainshadow-cec.c: In function 'rain_irq_work_handler':
drivers/media/usb/rainshadow-cec/rainshadow-cec.c:171:31: error: 'data' may be used uninitialized in this function [-Werror=maybe-uninitialized]

Slightly rearranging the code makes it easier for the compiler to see that the
code is correct, and gets rid of the warning.

Fixes: 0f314f6c

 ("[media] rainshadow-cec: new RainShadow Tech HDMI CEC driver")

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>