armv8/fsl-lsch3: consolidate the clock system initialization

This patch binds the sys_info->freq_systembus to Platform PLL, and
implements the IPs' clock function individually.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/include/configs/ls2080a_common.h b/include/configs/ls2080a_common.h
index eb628fd..32d56ae 100644
--- a/include/configs/ls2080a_common.h
+++ b/include/configs/ls2080a_common.h
@@ -97,7 +97,7 @@
 #define CONFIG_CONS_INDEX       1
 #define CONFIG_SYS_NS16550_SERIAL
 #define CONFIG_SYS_NS16550_REG_SIZE     1
-#define CONFIG_SYS_NS16550_CLK          (get_bus_freq(0)/2)
+#define CONFIG_SYS_NS16550_CLK          (get_serial_clock())
 
 #define CONFIG_BAUDRATE			115200
 #define CONFIG_SYS_BAUDRATE_TABLE	{ 9600, 19200, 38400, 57600, 115200 }