af_packet: de-inline some helper functions

This popped some compiler errors due to mismatched prototypes. Just
remove most manual inlines, the compiler should be able to figure out
what makes sense to inline and not.

net/packet/af_packet.c:252: warning: 'prb_curr_blk_in_use' declared inline after being called
net/packet/af_packet.c:252: warning: previous declaration of 'prb_curr_blk_in_use' was here
net/packet/af_packet.c:258: warning: 'prb_queue_frozen' declared inline after being called
net/packet/af_packet.c:258: warning: previous declaration of 'prb_queue_frozen' was here
net/packet/af_packet.c:248: warning: 'packet_previous_frame' declared inline after being called
net/packet/af_packet.c:248: warning: previous declaration of 'packet_previous_frame' was here
net/packet/af_packet.c:251: warning: 'packet_increment_head' declared inline after being called
net/packet/af_packet.c:251: warning: previous declaration of 'packet_increment_head' was here

Signed-off-by: Olof Johansson <olof@lixom.net>
Cc: Chetan Loke <loke.chetan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>