iwlwifi: move tx queue related code to separate file

Multiple iwlagn based devices shared the same tansmit queue functions.
Move tx queue related code from iwl-5000.c to iwl-agn-tx.c file.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/Makefile b/drivers/net/wireless/iwlwifi/Makefile
index 46fad2d..fec44cf 100644
--- a/drivers/net/wireless/iwlwifi/Makefile
+++ b/drivers/net/wireless/iwlwifi/Makefile
@@ -10,7 +10,7 @@
 # AGN
 obj-$(CONFIG_IWLAGN)	+= iwlagn.o
 iwlagn-objs		:= iwl-agn.o iwl-agn-rs.o iwl-agn-led.o iwl-agn-ict.o
-iwlagn-objs		+= iwl-agn-ucode.o iwl-agn-hcmd.o
+iwlagn-objs		+= iwl-agn-ucode.o iwl-agn-hcmd.o iwl-agn-tx.o
 
 iwlagn-$(CONFIG_IWL4965) += iwl-4965.o
 iwlagn-$(CONFIG_IWL5000) += iwl-5000.o