arm64: Save spsr in pt_regs

This register holds "pstate" which includes (among other things) the
instruction mode the CPU was in when the exception was taken. This is
necessary to correctly interpret instructions at elr.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
diff --git a/arch/arm/cpu/armv8/exceptions.S b/arch/arm/cpu/armv8/exceptions.S
index 001913f..504d566 100644
--- a/arch/arm/cpu/armv8/exceptions.S
+++ b/arch/arm/cpu/armv8/exceptions.S
@@ -77,15 +77,18 @@
 	switch_el x11, 3f, 2f, 1f
 3:	mrs	x1, esr_el3
 	mrs	x2, elr_el3
+	mrs	x3, spsr_el3
 	b	0f
 2:	mrs	x1, esr_el2
 	mrs	x2, elr_el2
+	mrs	x3, spsr_el2
 	b	0f
 1:	mrs	x1, esr_el1
 	mrs	x2, elr_el1
+	mrs	x3, spsr_el1
 0:
 	stp	x1, x0, [sp, #-16]!
-	stp	xzr, x2, [sp, #-16]!
+	stp	x3, x2, [sp, #-16]!
 	mov	x0, sp
 	ret