rt2x00: Centralize setting of extra TX headroom requested by rt2x00.

Set the value of extra_tx_headroom in a central place, rather than in each
of the drivers. This is preparatory for taking alignment space into account
in the TX headroom requested by rt2x00.

Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --cc drivers/net/wireless/rt2x00/rt2400pci.c
Simple merge

diff --cc drivers/net/wireless/rt2x00/rt2500pci.c
Simple merge

diff --cc drivers/net/wireless/rt2x00/rt2500usb.c
Simple merge

diff --cc drivers/net/wireless/rt2x00/rt2800lib.c
Simple merge

diff --cc drivers/net/wireless/rt2x00/rt2800pci.c
Simple merge

diff --cc drivers/net/wireless/rt2x00/rt2800usb.c
Simple merge

diff --cc drivers/net/wireless/rt2x00/rt2x00.h
Simple merge

diff --cc drivers/net/wireless/rt2x00/rt2x00dev.c
Simple merge

diff --cc drivers/net/wireless/rt2x00/rt61pci.c
Simple merge

diff --cc drivers/net/wireless/rt2x00/rt73usb.c
Simple merge