phy: cadence: Sierra: Model PLL_CMNLC and PLL_CMNLC1 as clocks (mux clocks)

Sierra has two PLLs, PLL_CMNLC and PLL_CMNLC1 and each of these PLLs has
two inputs, plllc_refclk (input from pll0_refclk) and refrcv (input from
pll1_refclk). Model PLL_CMNLC and PLL_CMNLC1 as clocks so that it's
possible to select one of these two inputs from device tree.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Reviewed-by: Swapnil Jakhade <sjakhade@cadence.com>
Link: https://lore.kernel.org/r/20210319124128.13308-13-kishon@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>