[ARM] Remove RETINSTR macro

RETINSTR is a left-over from the days when we had 26-bit and
32-bit CPU support integrated into the same tree.  Since this
is no longer the case, we can now remove RETINSTR.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/lib/memzero.S b/arch/arm/lib/memzero.S
index 51ccc60..764e7de 100644
--- a/arch/arm/lib/memzero.S
+++ b/arch/arm/lib/memzero.S
@@ -77,4 +77,4 @@
 	strneb	r2, [r0], #1		@ 1
 	tst	r1, #1			@ 1 a byte left over
 	strneb	r2, [r0], #1		@ 1
-	RETINSTR(mov,pc,lr)		@ 1
+	mov	pc, lr			@ 1