MFC r348179-r348182

r348179:
allwinner: aw_ccu: Add some debug printfs (disabled by default)

Also print information about setting frequency at boot under bootverbose

r348180:
arm: allwinner: clk: Add new clock aw_clk_frac

Add a clock driver for clock that can either be used in integer mode
with one N factor and one M divider or in fractional mode where the
output frequency is chosen between two predifined output.

r348181:
arm: allwinner: clk: Use the new frac clock

Some clocks used the NM type but this clock is for the ones with the
formula "clk = clkin / n / m" and not "clk = clkin * n / m"
Use the new frac clock for them.

r348182:
arm: allwinner: Remove frac mode from NM clk

We have a correct clock type aw_clk_frac now for this.