runtime: correctly negate errno value for *BSD ARM

Fixes #35037

Change-Id: I0b9bcd001556cd409994d83dabcdd6e32b001d28
Reviewed-on: https://go-review.googlesource.com/c/go/+/202441
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/runtime/sys_freebsd_arm.s

@@ -117,7 +117,7 @@ TEXT runtime·read(SB),NOSPLIT|NOFRAME,$0
 	MOVW n+8(FP), R2	// arg 3 count
 	MOVW $SYS_read, R7
 	SWI $0
-	SUB.CS	$0, R0, R0	// caller expects negative errno
+	RSB.CS	$0, R0		// caller expects negative errno
 	MOVW	R0, ret+12(FP)
 	RET
 
@@ -153,7 +153,7 @@ TEXT runtime·write1(SB),NOSPLIT|NOFRAME,$0
 	MOVW n+8(FP), R2	// arg 3 count
 	MOVW $SYS_write, R7
 	SWI $0
-	SUB.CS	$0, R0, R0	// caller expects negative errno
+	RSB.CS	$0, R0		// caller expects negative errno
 	MOVW	R0, ret+12(FP)
 	RET
 

src/runtime/sys_netbsd_arm.s

@@ -92,7 +92,7 @@ TEXT runtime·read(SB),NOSPLIT|NOFRAME,$0
 	MOVW p+4(FP), R1
 	MOVW n+8(FP), R2
 	SWI $SYS_read
-	SUB.CS	$0, R0, R0	// caller expects negative errno
+	RSB.CS	$0, R0		// caller expects negative errno
 	MOVW	R0, ret+12(FP)
 	RET
 
@@ -125,7 +125,7 @@ TEXT runtime·write1(SB),NOSPLIT|NOFRAME,$0
 	MOVW	p+4(FP), R1	// arg 2 - buf
 	MOVW	n+8(FP), R2	// arg 3 - nbyte
 	SWI $SYS_write
-	SUB.CS	$0, R0, R0	// caller expects negative errno
+	RSB.CS	$0, R0		// caller expects negative errno
 	MOVW	R0, ret+12(FP)
 	RET
 

src/runtime/sys_openbsd_arm.s

@@ -55,7 +55,7 @@ TEXT runtime·read(SB),NOSPLIT|NOFRAME,$0
 	MOVW	n+8(FP), R2		// arg 3 - nbyte
 	MOVW	$3, R12			// sys_read
 	SWI	$0
-	SUB.CS	$0, R0, R0	// caller expects negative errno
+	RSB.CS	$0, R0		// caller expects negative errno
 	MOVW	R0, ret+12(FP)
 	RET
 
@@ -82,7 +82,7 @@ TEXT runtime·write1(SB),NOSPLIT|NOFRAME,$0
 	MOVW	n+8(FP), R2		// arg 3 - nbyte
 	MOVW	$4, R12			// sys_write
 	SWI	$0
-	SUB.CS	$0, R0, R0	// caller expects negative errno
+	RSB.CS	$0, R0		// caller expects negative errno
 	MOVW	R0, ret+12(FP)
 	RET