net: arp: code cleanup

Clean the code up according to Documentation/CodingStyle.

Don't initialize the variable dont_send in arp_process().

Remove the temporary varialbe flags in arp_state_to_flags().
Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>