fix(intel): revert back to use L4 clock

Using mpu_peri as the clock source will caused the system
timer vary. System timer shall get from a static clock
source.

L4 and L3 clock are both the same at the moment.
There shall be a hardware update to differentiate the clock pll.
To keep this as dormant function for now.

Change-Id: I4d253e2f24a74cbec59bfcbf0e8547abbe3643a8
Signed-off-by: Jit Loon Lim <jit.loon.lim@intel.com>
Signed-off-by: Sieu Mun Tang <sieu.mun.tang@intel.com>
diff --git a/plat/intel/soc/stratix10/include/s10_clock_manager.h b/plat/intel/soc/stratix10/include/s10_clock_manager.h
index 790dbc1..c7632be 100644
--- a/plat/intel/soc/stratix10/include/s10_clock_manager.h
+++ b/plat/intel/soc/stratix10/include/s10_clock_manager.h
@@ -95,6 +95,7 @@
 uint32_t get_uart_clk(void);
 uint32_t get_mmc_clk(void);
 uint32_t get_l3_clk(uint32_t ref_clk);
+uint32_t get_cpu_clk(void);
 uint32_t get_ref_clk(uint32_t pllglob);
 uint32_t get_mpu_periph_clk(void);