[media] lme2510: do not use bInterfaceNumber from dvb_usb_v2

No need to access bInterfaceNumber via dvb_usb_v2 internals as driver
has it already.
That patch is prepare for dvb_usb_v2 deferred probe hack removal. It was
added due to udev firmware loading problems, but things are fixed after
that and it is not needed anymore.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>