Add function that zeros bits after prefix_len'th bit in an address.  Put
it in net.h so it can be use by both netconfig.c and icmp6.c,
potentially others.
---
 ell/net.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/ell/net.h b/ell/net.h
index 0521d75..e193eef 100644
--- a/ell/net.h
+++ b/ell/net.h
@@ -61,6 +61,19 @@ static inline bool l_net_prefix_matches(const void *a, const void *b,
 	return !bits || ((left ^ right) & (0xff00u >> bits)) == 0;
 }
 
+static inline void l_net_clear_host_bits(uint8_t *address, uint8_t prefix_len,
+						uint8_t bytes)
+{
+	uint8_t last_byte = prefix_len / 8;
+
+	if (prefix_len & 7) {
+		address[last_byte] &= 0xff00 >> (prefix_len & 7);
+		last_byte++;
+	}
+
+	memset(address + last_byte, 0, bytes - last_byte);
+}
+
 #ifdef __cplusplus
 }
 #endif
-- 
2.32.0