clk: sunxi: ccu-sun5i needs nkmp

A randconfig build ran into this rare link error:

drivers/clk/sunxi-ng/ccu-sun5i.o:(.data.__compound_literal.1+0x4): undefined reference to `ccu_nkmp_ops'
drivers/clk/sunxi-ng/ccu-sun5i.o:(.data.__compound_literal.7+0x4): undefined reference to `ccu_nkmp_ops'

This adds the missing 'select'.

Fixes: 5e737617

 ("clk: sunxi-ng: Add sun5i CCU driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>