iwlwifi: queue functions cleanup

This patch moves
1. iwl_queue_inc_wrap and int iwl_queue_dec_wrap
into  iwl-helpers.h these two functions are identical to common
for both iwl3956 and iwl4965
2. renames x2_queue_used to iwl3945_x2_queue_used
3. exports iwl3945_queue_space out of iwl3964-base.c

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-helpers.h b/drivers/net/wireless/iwlwifi/iwl-helpers.h
index 8993cca..736b888 100644
--- a/drivers/net/wireless/iwlwifi/iwl-helpers.h
+++ b/drivers/net/wireless/iwlwifi/iwl-helpers.h
@@ -254,6 +254,26 @@
 	return sizeof(addr) > sizeof(u32) ? (addr >> 16) >> 16 : 0;
 }
 
+/**
+ * iwl_queue_inc_wrap - increment queue index, wrap back to beginning
+ * @index -- current index
+ * @n_bd -- total number of entries in queue (must be power of 2)
+ */
+static inline int iwl_queue_inc_wrap(int index, int n_bd)
+{
+	return ++index & (n_bd - 1);
+}
+
+/**
+ * iwl_queue_dec_wrap - decrement queue index, wrap back to end
+ * @index -- current index
+ * @n_bd -- total number of entries in queue (must be power of 2)
+ */
+static inline int iwl_queue_dec_wrap(int index, int n_bd)
+{
+	return --index & (n_bd - 1);
+}
+
 /* TODO: Move fw_desc functions to iwl-pci.ko */
 static inline void iwl_free_fw_desc(struct pci_dev *pci_dev,
 				    struct fw_desc *desc)