media: atomisp: Remove duplication between runtime-pm and normal-pm code

atomisp_suspend() contains a 1:1 copy of atomisp_runtime_suspend() and
the same goes for the resume() functions.

Rename the runtime functions to atomisp_power_on()/_off() and use these
as runtime-pm handlers as well as helper in other places to remove
the code duplication.

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>