[media] gpio-ir-recv: a couple signedness bugs

There are couple places where we check unsigned values for negative.  I
changed ->gpin_nr to signed because in gpio_ir_recv_probe() we do:
        if (pdata->gpio_nr < 0)
                return -EINVAL;
I also change gval to a signed int in gpio_ir_recv_irq() because that's
the type that gpio_get_value_cansleep() returns and we test for negative
returns.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Trilok Soni <tsoni@codeaurora.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>