Enable pointer auth at EL2 and below

This patch disables EL3 traps for pointer auth functionality, such that
lower ELs can use it without requiring EL3 intervention.

We should check ID registers first, but this is good enough for testing.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
diff --git a/arch/aarch64/boot.S b/arch/aarch64/boot.S
index ceeee76..8069c43 100644
--- a/arch/aarch64/boot.S
+++ b/arch/aarch64/boot.S
@@ -38,6 +38,8 @@
 1:	mov	x0, #0x30			// RES1
 	orr	x0, x0, #(1 << 0)		// Non-secure EL1
 	orr	x0, x0, #(1 << 8)		// HVC enable
+	orr	x0, x0, #(1 << 16)		// AP key enable
+	orr	x0, x0, #(1 << 17)		// AP insn enable
 #ifndef KERNEL_32
 	orr	x0, x0, #(1 << 10)		// 64-bit EL2
 #endif