V4L/DVB (12432): em28xx: fix regression in Empire DualTV digital tuning

Restore support for digital tuning caused by regression during introduction
of disable_i2c_gate parameter to zl10353 driver.

Thanks to user "Xwang" for reporting the problem and testing the fix

Cc: Xwang <xwang1976@email.it>
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>