drm/xe/reg_sr: Simplify check for masked registers

For all RTP actions, clr_bits is a superset of the bits being modified.
That's also why the check for "changing all bits" can be done with
`clr_bits + 1`. So always use clr_bits for setting the upper bits of a
masked register.

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://lore.kernel.org/r/20230906012053.1733755-2-lucas.demarchi@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>