clk: sunxi-ng: h6: Fix clock divider range on some clocks

While comparing clocks between the H6 and H616, some of the M factor
ranges were found to be wrong: the manual says they are only covering
two bits [1:0], but our code had "5" in the number-of-bits field.

By writing 0xff into that register in U-Boot and via FEL, it could be
confirmed that bits [4:2] are indeed masked off, so the manual is right.

Change to number of bits in the affected clock's description.

Fixes: 524353ea ("clk: sunxi-ng: add support for the Allwinner H6 CCU")
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210118000912.28116-1-andre.przywara@arm.com