board/common/qemu: Downgrade CPU to Cortex-A53 on aarch64

This CPU has less emulation overhead than `max`, which is what we
mostly care about.

Author: wkz

board/common/qemu/Config.in.in

@@ -78,7 +78,7 @@ endchoice
 config QEMU_MACHINE
 	string "Select emulated machine"
 	default "qemu-system-arm     -M virt,accel=kvm:tcg -cpu max" if QEMU_arm
-	default "qemu-system-aarch64 -M virt,accel=kvm:tcg -cpu max,pauth-impdef=on" if QEMU_aarch64
+	default "qemu-system-aarch64 -M virt,accel=kvm:tcg -cpu cortex-a53" if QEMU_aarch64
 	default "qemu-system-x86_64  -M pc,accel=kvm:tcg   -cpu max" if QEMU_x86_64
 	help
 	  You should not have to change this setting, although you may