platform/x86/intel/pmc: Add missing extern

platform/x86/intel/pmc: Add missing extern

Add missing extern for tgl_h_reg_map. Fixes sparse warning:

  drivers/platform/x86/intel/pmc/tgl.c:213:26: warning: symbol 'tgl_h_reg_map' was not declared. Should it be static?

Fixes: 544f7b7f651c ("platform/x86/intel/pmc: Add regmap for Tiger Lake H PCH")
Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Link: https://lore.kernel.org/r/20231223032548.1680738-9-david.e.box@linux.intel.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>