clk: microchip: mpfs: delete 2 line mpfs_clk_register_foo()

The register functions are now comprised of only a single operation
each and no longer add anything to the driver. Delete them.

Reviewed-by: Daire McNamara <daire.mcnamara@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220909123123.2699583-12-conor.dooley@microchip.com