clk: sunxi-ng: mp: fix parent rate change flag check

CLK_SET_RATE_PARENT flag is checked on parent clock instead of current
one. Fix that.

Fixes: 3f790433

 ("clk: sunxi-ng: Adjust MP clock parent rate when allowed")
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Tested-by: Andre Heider <a.heider@gmail.com>
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Link: https://lore.kernel.org/r/20210209175900.7092-2-jernej.skrabec@siol.net


Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>