CLK: SPEAr13xx: Fix mux clock names

This patch updates mux clock names of multiple clocks. It updates _clk with
_mclk to make it more readable.

Signed-off-by: Shiraz Hashim <shiraz.hashim@st.com>
Signed-off-by: Rajeev Kumar <rajeev-dlh.kumar@st.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>