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.au


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>