kitakami-common: Set TARGET_2ND_CPU_VARIANT to cortex-a53

 * There is no cortex-a53.a57 specific routine since P
   according to commit f1d6e6e in bionic.

Change-Id: I3c6a2c9d08fa8d95288b6ac272912380a115e146

BoardConfigCommon.mk

@@ -40,7 +40,7 @@ TARGET_2ND_ARCH := arm
 TARGET_2ND_ARCH_VARIANT := armv8-a
 TARGET_2ND_CPU_ABI := armeabi-v7a
 TARGET_2ND_CPU_ABI2 := armeabi
-TARGET_2ND_CPU_VARIANT := cortex-a53.a57
+TARGET_2ND_CPU_VARIANT := cortex-a53
 
 TARGET_USES_64_BIT_BINDER := true
 TARGET_USES_64_BIT_BCMDHD := true