[bgpd] Fix compiler warnings related to MD5

This patch fixes:

bgp_network.c: In function 'bgp_md5_set':
bgp_network.c:107: warning: cast from pointer to integer of different size
bgp_network.c: In function 'bgp_socket':
bgp_network.c:447: warning: cast to pointer from integer of different size
1 file changed