media: i2c: adv748x: Fix test pattern selection mask

The mask to select the test-pattern in register ADV748X_SDP_FRP is
incorrect, it's the lower 3 bits which controls the pattern. The
GENMASK() macro is used incorrectly and the generated mask is 0x0e
instead of 0x07.

The result is that not all test patterns are selectable, and that in
some cases the wrong test pattern is activated. Fix this by correcting
the GENMASK().

Fixes: 3e89586a ("media: i2c: adv748x: add adv748x driver")
Cc: stable@vger.kernel.org
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
[hverkuil: fixed tiny typo in commit log: my -> by]