clk: xgene: Add SoC and PMD PLL clocks with v2 hardware

Add X-Gene SoC and PMD PLL clocks support for v2 hardware.
X-Gene SoC v2 and above use an slightly different SoC
and PMD PLL hardware logic.

Signed-off-by: Loc Ho <lho@apm.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>