doc: correct orthography, word forms and missing/extraneous words

src/libsystemd-network/lldp-tlv.c

@@ -278,7 +278,7 @@ int tlv_packet_parse_pdu(tlv_packet *m, uint16_t size) {
 
         p = m->pdu;
 
-        /* extract ethernet header */
+        /* extract Ethernet header */
         memcpy(&m->mac, p, ETH_ALEN);
         p += sizeof(struct ether_header);
 

src/libsystemd-network/sd-dhcp-client.c

@@ -1517,7 +1517,7 @@ static int client_receive_message_udp(sd_event_source *s, int fd,
                 expected_hlen = ETH_ALEN;
                 expected_chaddr = (const struct ether_addr *) &client->mac_addr;
         } else {
-               /* Non-ethernet links expect zero chaddr */
+               /* Non-Ethernet links expect zero chaddr */
                expected_hlen = 0;
                expected_chaddr = &zero_mac;
         }

src/libsystemd-network/test-lldp.c

@@ -54,7 +54,7 @@ static int lldp_build_tlv_packet(tlv_packet **ret) {
                 .ether_type = htons(ETHERTYPE_LLDP),
         };
 
-        /* Append ethernet header */
+        /* Append Ethernet header */
         memcpy(&ether.ether_dhost, lldp_dst, ETHER_ADDR_LEN);
         memcpy(&ether.ether_shost, &mac_addr, ETHER_ADDR_LEN);