unix: add race annotations to Pread and Pwrite

Follow CL 391954 which changed Pread/Pwrite in package syscall.

For golang/go#51618

Change-Id: Icc587c61f083886bb66ca96717f686f56b398e34
Reviewed-on: https://go-review.googlesource.com/c/sys/+/392794
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/unix/zsyscall_openbsd_arm.go b/unix/zsyscall_openbsd_arm.go
index 883a9b4..69f8030 100644
--- a/unix/zsyscall_openbsd_arm.go
+++ b/unix/zsyscall_openbsd_arm.go
@@ -1128,7 +1128,7 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func Pread(fd int, p []byte, offset int64) (n int, err error) {
+func pread(fd int, p []byte, offset int64) (n int, err error) {
 	var _p0 unsafe.Pointer
 	if len(p) > 0 {
 		_p0 = unsafe.Pointer(&p[0])
@@ -1145,7 +1145,7 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func Pwrite(fd int, p []byte, offset int64) (n int, err error) {
+func pwrite(fd int, p []byte, offset int64) (n int, err error) {
 	var _p0 unsafe.Pointer
 	if len(p) > 0 {
 		_p0 = unsafe.Pointer(&p[0])