clk: sunxi-ng: enable SUNXI_CCU_MP for PRCM

The newly added PRCM CCU driver uses SUNXI_CCU_MP_WITH_MUX_GATE, which causes
a link error when no other driver enables SUNXI_CCU_MP:

drivers/clk/built-in.o:(.data+0x5c8c8): undefined reference to `ccu_mp_ops'

This adds an explicit 'select' statement for it.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

drivers/clk/sunxi-ng/Kconfig

@@ -156,6 +156,7 @@ config SUN8I_R_CCU
 	bool "Support for Allwinner SoCs' PRCM CCUs"
 	select SUNXI_CCU_DIV
 	select SUNXI_CCU_GATE
+	select SUNXI_CCU_MP
 	default MACH_SUN8I || (ARCH_SUNXI && ARM64)
 
 endif