drm/i915/psr: Wrap PSR1 register with functions

In preparation for re-introducing HSW's different PSR1 register
offeets let's just wrap all the registers into functions.
Avoids having to make the register macros more complex.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230609141404.12729-4-ville.syrjala@linux.intel.com


Reviewed-by: Jouni Högander <jouni.hogander@intel.com>