Rename all USB drivers with their own directory under
drivers/media/video into drivers/media/usb and update the
building system.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

b2c2 is, in fact, 2 drivers: one for PCI and one for USB, plus
a common bus-independent code. Break it accordingly.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

As media/dvb will be removed, move it to a proper place.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>