Function ostd::trap::enable_local

pub fn enable_local()

Enables all IRQs on the current CPU.

FIXME: The reason we need to add this API is that currently IRQs are enabled when the CPU enters the user space for the first time, which is too late. During the OS initialization phase, we need to get the block device working and mount the filesystems, thus requiring the IRQs should be enabled as early as possible.

FIXME: this method may be unsound.