Fix the following warnings:
	drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1146 gen_twopix() error: buffer overflow 'buf[1]' 8 <= 8
	drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1152 gen_twopix() error: buffer overflow 'buf[1]' 8 <= 8
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>