iwlwifi: rename functions in transport layer

1) s/tx_queue/txq
	for the sake of consistency.

2) s/rx_queue/rxq
	for the sake of consistency.

3) Make all functions begin with iwl_pcie_
	iwl_queue_init and iwl_queue_space are an exception
	since they are not PCIE specific although they are in
	pcie subdir.

4) s/trans_pcie_get_cmd_string/get_cmd_string
	it is much shorter and used in debug prints which
	are long lines.

5) s/iwl_bg_rx_replenish/iwl_pcie_rx_replenish_work
	this better emphasizes that it is a work

6) remove invalid kernelDOC markers

pcie/tx.c and pcie/trans.c still needs to be cleaned up.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>