V4L/DVB (8685): mt9m001, mt9v022: Simplify return code checking

i2c_smbus_write_word_data() returns 0 or a negative error, hence no need to
check for "> 0".

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>