irq_work: register irq_work_cpu_notify in early init

Currently irq_work_cpu_notify is registered using
device_initcall().

In cases where CPU is hotplugged early (example
would be thermal engine hotplugging CPU), there
are chances where irq_work_cpu_notifier has not
even registered, but CPU is already hotplugged out.
irq_work uses CPU_DYING notifier to clear out the
pending irq_work. But since the cpu notifier is not
even registered that early, pending irq_work
items are never run since this pending list is
percpu.

One specific scenario where this is impacting
the system is, rcu framework using irq_work
to wakeup and complete cleanup operations. In this
scenario we notice that RCU operations needs cleanup
on the hotplugged CPU.

Fix this by registering irq_work_cpu_notify
in early init.

CRs-Fixed: 768180
Change-Id: Ibe7f5c77097de7a342eeb1e8d597fb2f72185ecf
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: Vignesh Radhakrishnan <vigneshr@codeaurora.org>