dmaengine: mv_xor_v2: Use some clk_ helper functions to simplify code

Use devm_clk_get_[optional_]enabled() instead of hand writing it.
It saves some LoC.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/cc14e490f4e6002a17c9c7d283fe6a93179766c2.1679814350.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Vinod Koul <vkoul@kernel.org>