drm/i915: Use REG_BIT() & co. for gen9+ timestamp freq registers

Convert the gen9+ timestamo frequency related registers to
the modern REG_BIT()/etc. style.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250211231941.22769-12-ville.syrjala@linux.intel.com