efi: Allow to expose the workqueue via sysfs

efi: Allow to expose the workqueue via sysfs

Exposing the efi_rts_wq workqueue via sysfs provides an easy mechanism
to restrict EFI firmware invocation to certain CPU(s).
This can be used to restrict EFI invocations to specific CPUs while
allowing other workqueue to use the remaning CPUs.

Expose the workqueue via sysfs. Change the name to efi_runtime which is
what will be visible under sysfs.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>