syscall: use actual free register

arch/at91sam3x8e/syscall.S

@@ -20,12 +20,12 @@ syscall:
 	 * OF GCC WHEN COMPILING SOME C CODE.  BUT AT THIS POINT, I WON'T EVEN
 	 * BOTHER WITH WHATEVER SHITTY COMPILE OPTION OR PREPROCESSOR DIRECTIVE
 	 * I HAVE TO TURN ON IN ORDER FOR THIS PIECE OF SHIT THAT DARES CALLING
-	 * ITSELF A COMPILER EAT MY SHIT CODE AND SHITS OUT THE SHITTY BINARY
-	 * I WANT.  FUCK YOU, SYSCALLS WILL JUST TAKE 10 INSTRUCTIONS MORE THEN.
+	 * ITSELF A COMPILER TO EAT MY SHIT CODE AND SHIT OUT THE SHITTY BINARY
+	 * I WANT.  FUCK YOU, SYSCALLS WILL JUST TAKE 8 INSTRUCTIONS MORE.
 	 */
 
-	mov	r3,	r12
-	push	{r3}
+	mov	r4,	r12
+	push	{r4}
 
 	mov	r12,	r0		/* syscall number */
 	mov	r7,	r12