clk: microchip: mpfs: convert cfg_clk to clk_divider

The cfg_clk struct is now just a redefinition of the clk_divider struct
with custom implentations of the ops, that implement an extra level of
redirection. Remove the custom struct and replace it with clk_divider.

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/20220909123123.2699583-13-conor.dooley@microchip.com