drm/xe/xe3p_xpc: Treat all PSMI MCR ranges as "INSTANCE0"

drm/xe/xe3p_xpc: Treat all PSMI MCR ranges as "INSTANCE0"

Early versions of the B-spec originally indicated that Xe3p_XPC had two
ranges of PSMI registers requiring MCR steering (one starting at 0xB500,
one starting at 0xB600), and that reads of registers in these ranges
required different grpid values to ensure that a non-terminated value is
obtained.  A late-breaking spec update has simplified this; both ranges
can be safely steered to grpid=0 for reads.

Drop the "PSMI19" replication type and related code, and consolidate
both register ranges into a single entry in the "INSTANCE0" steering
table.

Bspec: 74418
Fixes: be614ea19dad ("drm/xe/xe3p_xpc: Add MCR steering")
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20251021224556.437970-2-matthew.d.roper@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>