staging: gdm724x: Place macro argument within parentheses

Place the macro arguments within parentheses to avoid precedence issues.
This solves the following checkpatch.pl warnings

CHECK: Macro argument 'len' may be better as '(len)' to avoid precedence issues
+#define ND_NLMSG_S_LEN(len)    (len + ND_IFINDEX_LEN)

CHECK: Macro argument 'nlh' may be better as '(nlh)' to avoid precedence issues
+#define ND_NLMSG_R_LEN(nlh)    (nlh->nlmsg_len - ND_IFINDEX_LEN)
Signed-off-by: Dee-Jay Anthony Logozzo <dj@djl.id.au>
Link: https://lore.kernel.org/r/20210811134132.5240-1-dj@djl.id.auSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/gdm724x/netlink_k.c

@@ -19,8 +19,8 @@ static DEFINE_MUTEX(netlink_mutex);
 #define ND_NLMSG_SPACE(len)	(NLMSG_SPACE(len) + ND_IFINDEX_LEN)
 #define ND_NLMSG_DATA(nlh)	((void *)((char *)NLMSG_DATA(nlh) + \
 						  ND_IFINDEX_LEN))
-#define ND_NLMSG_S_LEN(len)	(len + ND_IFINDEX_LEN)
-#define ND_NLMSG_R_LEN(nlh)	(nlh->nlmsg_len - ND_IFINDEX_LEN)
+#define ND_NLMSG_S_LEN(len)	((len) + ND_IFINDEX_LEN)
+#define ND_NLMSG_R_LEN(nlh)	((nlh)->nlmsg_len - ND_IFINDEX_LEN)
 #define ND_NLMSG_IFIDX(nlh)	NLMSG_DATA(nlh)
 #define ND_MAX_MSG_LEN		(1024 * 32)