staging: hi6421-spmi-pmic: use devm_request_threaded_irq()

Use devm_request_threaded_irq() in order to simplify the
driver.

Suggested-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/b47827c3466eeef3a7de6ac56b1fe93b5ff84e30.1624606660.git.mchehab+huawei@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>