rv30: fix masking in rv30_loop_filter()

The mask `x && (1 << y)' is incorrect and always yields true.

The correct form should be `x & (1 << y)'.

CC: libav-stable@libav.org

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>