[media] cx23885-dvb: remove previously overriden value

drivers/media/pci/cx23885/cx23885-dvb.c:768:2: warning: initialized field overwritten [-Woverride-init]
  .freq_offset_khz_vhf = 550,
  ^
drivers/media/pci/cx23885/cx23885-dvb.c:768:2: warning: (near initialization for 'dib7070p_dib0070_config.freq_offset_khz_vhf') [-Woverride-init]

Cc: James Harper <james.harper@ejbdigital.com.au>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>