p54usb: Fixes compile error with CONFIG_PM=n

/drivers/net/wireless/p54/p54usb.c: In function 'p54u_probe':
/drivers/net/wireless/p54/p54usb.c:923: error: 'struct usb_device' has no member named 'reset_resume'

In the struct usb_device the reset_resume attribute is only available
when CONFIG_PM is defined.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>