core: thread: fix unaligned stack pointer

Fixes unaligned stack pointer in __thread_enter_user_mode. The
stack pointer must always be 8 byte aligned when entering a new
function.

Reviewed-by: Joakim Bech <joakim.bech@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

Author: jenswi-linaro

core/arch/arm/kernel/thread_a32.S

@@ -522,7 +522,7 @@ UNWIND(	.cantunwind)
 	mov	r6, sp
 	mov     sp, r4
 	cps	#CPSR_MODE_SVC
-	push	{r6}
+	push	{r6,r7}
 
 	/*
 	* Don't allow return from this function, return is done through
@@ -542,13 +542,13 @@ END_FUNC __thread_enter_user_mode
 FUNC thread_unwind_user_mode , :
 UNWIND(	.fnstart)
 UNWIND(	.cantunwind)
-	ldr     ip, [sp, #(14 * 0x4)]   /* &ctx->panicked */
+	ldr     ip, [sp, #(15 * 0x4)]   /* &ctx->panicked */
 	str	r1, [ip]
-	ldr     ip, [sp, #(15 * 0x4)]   /* &ctx->panic_code */
+	ldr     ip, [sp, #(16 * 0x4)]   /* &ctx->panic_code */
 	str	r2, [ip]
 
 	/* Restore old user sp */
-	pop	{r4}
+	pop	{r4,r7}
 	cps	#CPSR_MODE_SYS
 	mov	sp, r4
 	cps	#CPSR_MODE_SVC