Revert "iwlwifi: move _agn statistics related structure"

This reverts commit a2064b7a.

when CONFIG_IWLAGN=n:

drivers/net/wireless/iwlwifi/iwl-rx.c:254: error: 'struct iwl_priv' has no member named '_agn'
drivers/net/wireless/iwlwifi/iwl-rx.c:303: error: 'struct iwl_priv' has no member named '_agn'
drivers/net/wireless/iwlwifi/iwl-rx.c:304: error: 'struct iwl_priv' has no member named '_agn'
drivers/net/wireless/iwlwifi/iwl-rx.c:305: error: 'struct iwl_priv' has no member named '_agn'
drivers/net/wireless/iwlwifi/iwl-rx.c:306: error: 'struct iwl_priv' has no member named '_agn'

and many more.

Conflicts:

	drivers/net/wireless/iwlwifi/iwl-agn-debugfs.c
	drivers/net/wireless/iwlwifi/iwl-debugfs.c
	drivers/net/wireless/iwlwifi/iwl-dev.h
	drivers/net/wireless/iwlwifi/iwl-rx.c

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>