clk: sunxi: Remove ahb1_sdram from sun6i/sun8i protected clocks list

The ahb1_sdram clock gate is only used for accessing the sdram
controller's registers over the bus. It is not used for actually clock
the controller or the dram, hence it does not need to be protected.

This also gets rid of the problem when the protected ahb1_sdram gate
is prepared/enabled while it is still an orphan, and the operation
is not propagated to the correct parent.

This was confirmed on my A23 tablet and my A31 Hummingbird.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>