media: camss: vfe: simplify vfe_get_wm_sizes()

media: camss: vfe: simplify vfe_get_wm_sizes()

Static analysis reports this representative problem
camss-vfe-4-1.c:333: The result of the left shift is undefined because
  the left operand is negative
  reg |= (height - 1) << 4;
~~~~~~~~~ ^

The is a false positive.  height is set in vfe_get_wm_sizes() which
has a switch statement without a default.

Reviewing the switch, the cases contain redundant assignments.
So simplify to assignments.

Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>