clk: uniphier: Add SoC-glue clock source selector support for Pro4

Add SoC-glue clock source selector for ahci controller on UniPhier SoCs.
Currently this supports Pro4 only.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Link: https://lore.kernel.org/r/1634000035-3114-6-git-send-email-hayashi.kunihiko@socionext.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
