Input: gpio-keys - fix a sleep while atomic with PREEMPT_RT

In the Linux kernel, the following vulnerability has been resolved:

Input: gpio-keys - fix a sleep while atomic with PREEMPT_RT

When enabling PREEMPT_RT, the gpio_keys_irq_timer() callback runs in

hard irq context, but the input_event() takes a spin_lock, which isn't

allowed there as it is converted to a rt_spin_lock().

[ 4054.289999] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48

[ 4054.290028] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/0

...

[ 4054.290195] __might_resched+0x13c/0x1f4

[ 4054.290209] rt_spin_lock+0x54/0x11c

[ 4054.290219] input_event+0x48/0x80

[ 4054.290230] gpio_keys_irq_timer+0x4c/0x78

[ 4054.290243] __hrtimer_run_queues+0x1a4/0x438

[ 4054.290257] hrtimer_interrupt+0xe4/0x240

[ 4054.290269] arch_timer_handler_phys+0x2c/0x44

[ 4054.290283] handle_percpu_devid_irq+0x8c/0x14c

[ 4054.290297] handle_irq_desc+0x40/0x58

[ 4054.290307] generic_handle_domain_irq+0x1c/0x28

[ 4054.290316] gic_handle_irq+0x44/0xcc

Considering the gpio_keys_irq_isr() can run in any context, e.g. it can

be threaded, it seems there's no point in requesting the timer isr to

run in hard irq context.

Relax the hrtimer not to use the hard context.