drm/i915: Reoder gen9+ timestamp freq register bits

We customarily define the bits of a register in big endian
order. Reorder the gen9+ timestamp freq register bits to match.

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/20250211231941.22769-13-ville.syrjala@linux.intel.com