timer_settime

arm/disarm and fetch state of POSIX per-process timer

sys_timer_settime(timer_t timer_id, int flags, const struct __kernel_itimerspec *new_setting, struct __kernel_itimerspec *old_setting)

register	value
`a7`	110, the syscall number
`a0`	timer_t timer_id
`a1`	int flags
`a2`	const struct __kernel_itimerspec *new_setting
`a3`	struct __kernel_itimerspec *old_setting
`a0`	the return value

Then run ecall to enter the kernel.

Same syscall on other architectures