media: atomisp: Remove atomisp_ospm_dphy_up()/_down() functions

atomisp_ospm_dphy_up() is an empty function now and
atomisp_ospm_dphy_down() contains a couple of checks + goto done
statements which don't matter since the function always ends up at
the done label regardless and then it does 1 pci-config write.

Move the single pci-config write directly to atomisp_power_off()
and remove the atomisp_ospm_dphy_up()/_down() functions.

Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>