V4L/DVB (12100): em28xx: make sure the analog GPIOs are set if we used a card hint

In cases where the board had a default USB ID, we would not indentify the
board until after the call to em28xx_set_mode().  As a result, for those
boards the analog GPIOs were not being set before probing the i2c bus for
devices (the probe would occur with the GPIOs being all high).

Make a call to em28xx_set_mode() so that the GPIOs are set properly before
probing the i2c bus for devices.

This problem was detected with the EVGA inDtube, where the tvp5150 is not
powered on unless GPIO1 is pulled low.

Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>