media: atomisp: properly parse CLK PMIC on newer devices

Newer devices don't place the PMIC CLK line inside an EFI
var. Instead, those are found at the _PR0 table.

Add a parser for it, using info stored via the DSDT table.

Tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>