media: Hantro: Correct G2 init qp field

Documentation said that g2 init_qp field use bits 24 to 30 of
the 8th register.
Change the field mask to be able to set 7 bits and not only 6 of them.

Conformance test INITQP_B_Main10_Sony_1 decoding is OK with this
patch.

Fixes: cb5dd5a0

 ("media: hantro: Introduce G2/HEVC decoder")
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>