mtd: rawnand: sunxi: remove usage of struct sunxi_ccm_reg

mtd: rawnand: sunxi: remove usage of struct sunxi_ccm_reg

The sunxi_ccm_reg is legacy, drop its usage from nand related code

For that, CCU_NAND0_CLK_CFG and CCU_AHB_GATE1 are added to the clock
files when missing.
And clock code in sunxi_nand{,_spl}.c and board.c are changed to use the
new scheme.

Moreover, drop AHB_DIV_1 in favor of the more readable CCM_NAND_CTRL_M/N

Suggested-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Richard Genoud <richard.genoud@bootlin.com>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>