V4L/DVB (13581): DiBUSB: fix I2c access when there is a read-access w/o write sequence

This patch fixes the behaviour of the dibusb-i2c-access which was previously changed to avoid accidental EEprom writes:

Now it allow i2c-reads without prepended i2c-writes, but it is still not doing anything in case the EEprom is addressed.

Thanks to Mario Bachmann for testing.

Tested-by: Mario Bachmann <grafgrimm77@gmx.de>
Cc: Mario Bachmann <grafgrimm77@gmx.de>
Signed-off-by: Patrick Boettcher <pboettcher@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>