internal/bytealg: fix arm64 Index function

Missed removing the argument loading from the indexbody function.

Change-Id: Ia1391231fc99771d00410a09fe80a09f08ceed02
Reviewed-on: https://go-review.googlesource.com/98575
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/internal/bytealg/index_arm64.s

@@ -31,10 +31,6 @@ TEXT indexbody<>(SB),NOSPLIT,$0-56
 	// main idea is to load 'sep' into separate register(s)
 	// to avoid repeatedly re-load it again and again
 	// for sebsequent substring comparisons
-	MOVD	a_base+0(FP), R0
-	MOVD	a_len+8(FP), R1
-	MOVD	b_base+24(FP), R2
-	MOVD	b_len+32(FP), R3
 	SUB	R3, R1, R4
 	// R4 contains the start of last substring for comparsion
 	ADD	R0, R4, R4