em28xx: Make all em28xx extensions to be initialized asynchronously

em28xx: Make all em28xx extensions to be initialized asynchronously

commit 6ae5e060840589f567c1837613e8a9d34fc9188a upstream.

em28xx-dvb, em28xx-alsa and em28xx-ir are typically initialized
asyncrhronously. The exception for it is when those modules
are loaded before em28xx (or before an em28xx card insertion) or
when they're built in.

Make the extentions to always load asynchronously. That allows
having all DVB firmwares loaded synchronously with udev-182.

Antti tested it with the following hardware:
	Hauppauge WinTV HVR 930C
	MaxMedia UB425-TC
	PCTV QuatroStick nano (520e)

Tested-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>