[media] lgdt330x: fix signedness error in i2c_read_demod_bytes()

The error handling in lgdt3303_read_status() and lgdt330x_read_ucblocks()
doesn't work, because i2c_read_demod_bytes() returns a u8 and (err < 0)
is always false.

        err = i2c_read_demod_bytes(state, 0x58, buf, 1);
        if (err < 0)
                return err;

Change the return type of i2c_read_demod_bytes() to int.  Also change
the return value on error to -EIO to make (err < 0) work.

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>