clk: qcom: Add A53 PLL support

The CPUs on Qualcomm MSM8916-based platforms are clocked by two PLLs,
a primary (A53) CPU PLL and a secondary fixed-rate GPLL0. These sources
are connected to a mux and half-integer divider, which is feeding the
CPU cores.

This patch adds support for the primary CPU PLL which generates the
higher range of frequencies above 1GHz.

Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>