PCI: aerdrv: cleanup inconsistent functions

This cleanup solves some minor naming issues by removing unuseful
function aer_delete_rootport() and by renaming disable_root_aer()
to aer_disable_rootport().

- Inconsistent location of alloc & free:
   The struct rpc is allocated in aer_alloc_rpc() at aerdrv.c
   while it is implicitly freed in aer_delete_rootport() at
   aerdrv_core.c.

- Inconsistent function name:
   It makes a bit confusion that aer_delete_rootport() is seemed
   to be paired with aer_enable_rootport(), i.e. there is neither
   "add" against "delete" nor "disable" against "enable".

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Reviewed-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>