util/nvmutil: Use correct pledge promise (OpenBSD)

I assumed wpath was all that's needed, but this simply
allows writes.

rpath must be specified alongside wpath, for reads.

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/nvmutil/nvmutil.c

@@ -84,7 +84,7 @@ main(int argc, char *argv[])
 	const char *strMac = NULL, *strRMac = "??:??:??:??:??:??";
 
 #ifdef __OpenBSD__
-	if (pledge("stdio wpath", NULL) == -1)
+	if (pledge("stdio rpath wpath", NULL) == -1)
 		err(errno, "pledge");
 #endif