[media] cx25840/cx18: Use standard ordering of mask and shift

Precedence of & and >> is not the same and is not left to right.
shift has higher precedence and should be done after the mask.

This use has a mask then shift which is not the normal style.

Move the shift before the mask to match nearly all the other
uses in kernel.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>