net/eth: fix incorrect check of iov_to_buf() return value

So we have sizeof(struct in6_address) != sizeof(uintptr_t)
and Clang > Coverity on this, see 4555ca68 :)

net/eth.c:426:30: warning: The code calls sizeof() on a pointer type. This can produce an unexpected result
        return bytes_read == sizeof(dst_addr);
                             ^     ~~~~~~~~~~
net/eth.c:475:34: warning: The code calls sizeof() on a pointer type. This can produce an unexpected result
            return bytes_read == sizeof(src_addr);
                                 ^     ~~~~~~~~~~

Reported-by: Clang Static Analyzer
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Dmitry Fleytman <dmitry@daynix.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

net/eth.c

@@ -423,7 +423,7 @@ _eth_get_rss_ex_dst_addr(const struct iovec *pkt, int pkt_frags,
                                 rthdr_offset + sizeof(*ext_hdr),
                                 dst_addr, sizeof(*dst_addr));
 
-        return bytes_read == sizeof(dst_addr);
+        return bytes_read == sizeof(*dst_addr);
     }
 
     return false;
@@ -472,7 +472,7 @@ _eth_get_rss_ex_src_addr(const struct iovec *pkt, int pkt_frags,
                                     opt_offset + sizeof(opthdr),
                                     src_addr, sizeof(*src_addr));
 
-            return bytes_read == sizeof(src_addr);
+            return bytes_read == sizeof(*src_addr);
         }
 
         opt_offset += optlen;