V4L/DVB (9155): em28xx-dvb: dvb_init() code factorization

In dvb_init(),
        case EM2880_BOARD_TERRATEC_HYBRID_XS:
        case EM2880_BOARD_KWORLD_DVB_310U:
can be put in the same case than EM2880_BOARD_HAUPPAUGE_WINTV_HVR_900
since they do the same thing.

Signed-off-by: Thierry MERLE <thierry.merle@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>