media: qcom: camss: Make function vfe_set_selection static

The function vfe_set_selection is local to the source and does
not need to be in global scope, so make it static.

Cleans up sparse warning:
warning: symbol 'vfe_set_selection' was not declared. Should it be static?

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Todor Tomov <todor.tomov@linaro.org>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>