Staging: wlan-ng: Add missing argument

The commit c8442118 introduced a struct wireless_dev pointer
as a second argument of the function pointers set_tx_power
and get_tx_power. This patch adds the missing arguments for
the wlan-ng driver.

Sparse warnings:

drivers/staging/wlan-ng/cfg80211.c:735:25: warning:
	incorrect type in initializer (incompatible argument 2
	(different base types))
	drivers/staging/wlan-ng/cfg80211.c:735:25:
	expected int ( *set_tx_power )( ... )
	drivers/staging/wlan-ng/cfg80211.c:735:25:
	got int ( extern [toplevel] *<noident> )( ... )

drivers/staging/wlan-ng/cfg80211.c:736:25: warning:
	incorrect type in initializer (incompatible argument 2
	(different base types))
	drivers/staging/wlan-ng/cfg80211.c:736:25:
	expected int ( *get_tx_power )( ... )
	drivers/staging/wlan-ng/cfg80211.c:736:25:
	got int ( extern [toplevel] *<noident> )( ... )

drivers/staging/wlan-ng/cfg80211.c:735:2: warning:
	initialization from incompatible pointer type [enabled by default]

drivers/staging/wlan-ng/cfg80211.c:735:2: warning:
	(near initialization for ‘prism2_usb_cfg_ops.set_tx_power’)
	[enabled by default]

drivers/staging/wlan-ng/cfg80211.c:736:2: warning:
	initialization from incompatible pointer type [enabled by default]

drivers/staging/wlan-ng/cfg80211.c:736:2: warning:
	(near initialization for ‘prism2_usb_cfg_ops.get_tx_power’)
	[enabled by default]

Signed-off-by: Emil Goode <emilgoode@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>