[media] s5h1420: Unused variable clock_setting

The switch/case was setting clock_setting that is not being used. Both switch/case and the variable definition were removed.

Currently clock is being calculated by the formula:
(state->fclk/1000000 - 8)

Tested by compilation only.

Signed-off-by: Peter Senna Tschudin <peter.senna@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>