thermal: rcar_gen3_thermal: fix interrupt type

Currently IRQF_SHARED type interrupt line is allocated, but it
is not appropriate, as the interrupt line isn't shared between
different devices, instead IRQF_ONESHOT is the proper type.

By changing interrupt type to IRQF_ONESHOT, now irq handler is
no longer needed, as clear of interrupt status can be done in
threaded interrupt context.

Because IRQF_ONESHOT type interrupt line is kept disabled until
the threaded handler has been run, so there is no need to protect
read/write of REG_GEN3_IRQSTR with lock.

Fixes: 7d4b2697 ("enable hardware interrupts for trip points")
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Tested-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>