media: tc358743: initialize variable

clang static analysis flags this error

tc358743.c:1468:9: warning: Branch condition evaluates
  to a garbage value
        return handled ? IRQ_HANDLED : IRQ_NONE;
               ^~~~~~~
handled should be initialized to false.

Fixes: d747b806 ("[media] tc358743: add direct interrupt handling")
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>