drxk: allow loading firmware synchrousnously

Due to udev-182, the firmware load was changed to be async, as
otherwise udev would give up of loading a firmware.

Add an option to return to the previous behaviour, async firmware
loads cause failures with the tda18271 driver.

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>
Cc: stable@kernel.org #	for Kernel 3.6 - please note that driver location has changed
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>