phy: cadence: Sierra: Move all clk_get_*() to a separate function

No functional change. Group all devm_clk_get_optional() to a
separate function.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Reviewed-by: Swapnil Jakhade <sjakhade@cadence.com>
Link: https://lore.kernel.org/r/20210319124128.13308-6-kishon@ti.com


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