media: tda9840: cleanup a warning

There's a false positive warning there:
	drivers/media/i2c/tda9840.c:79 tda9840_status() error: uninitialized symbol 'byte'.

Change the code to match our coding style, in order to fix it.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>