sys_clk has multiple parents and selection of parent depends on sys_clk_ctrl
register bit no. 23:25, with following possibilities

   0XX: pll1_clk
   10X: sys_synth_clk
   110: pll2_clk
   111: pll3_clk

Out of several possibilities (h/w wise) to select same clock parent for
sys_clk, current clock implementation was considering just one value.

When bootloader programmed different (valid) value to select a clock
parent then Linux breaks.

Here, we try to include all possibilities which can lead to same
clock selection thus making Linux independent of bootloader selection
values.
Signed-off-by: NVipul Kumar Samar <vipulkumar.samar@st.com>
Signed-off-by: NShiraz Hashim <shiraz.hashim@st.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>