clk: arm64: Add DTS clock entry for APM X-Gene Storm SoC

clk: arm64: Add DTS clock entry for APM X-Gene Storm SoC with reference to
reference, PCP PLL, SoC PLL, and Ethernet clocks.

Signed-off-by: Loc Ho <lho@apm.com>
Signed-off-by: Kumar Sankaran <ksankaran@apm.com>
Signed-off-by: Vinayak Kale <vkale@apm.com>
Signed-off-by: Feng Kan <fkan@apm.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>