Input: cma3000_d0x - fix signedness bug in cma3000_thread_irq()

The error check (intr_status < 0) didn't work because intr_status is
a u8.  Change its type to signed int.

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>