arm64: fsl: layerscape: Remove unused functions

Function board_switch_core_volt has not been used since it was
defined

Signed-off-by: Shenlin Liang <liangshenlin@eswincomputing.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/cpu/armv8/fsl-layerscape/soc.c b/arch/arm/cpu/armv8/fsl-layerscape/soc.c
index 577a0b6..3bfdc3f 100644
--- a/arch/arm/cpu/armv8/fsl-layerscape/soc.c
+++ b/arch/arm/cpu/armv8/fsl-layerscape/soc.c
@@ -575,11 +575,6 @@
 	return vdd;
 }
 
-__weak int board_switch_core_volt(u32 vdd)
-{
-	return 0;
-}
-
 static int setup_core_volt(u32 vdd)
 {
 	return board_setup_core_volt(vdd);