[media] hackrf: harmless off by one in debug code

My static checker complains that "i" could be one element beyond the end
of the array.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>