drm/xe/hwmon: Remove xe_hwmon_process_reg

Remove xe_hwmon_process_reg as it is a umbrella function which can be
avoided (Lucas).

v2: Improve commit message. (Badal)

v3: Add couple of comments. (Lucas)

Signed-off-by: Karthik Poosa <karthik.poosa@intel.com>
Suggested-by: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Badal Nilawar <badal.nilawar@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240626170746.2926011-2-karthik.poosa@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>