feat(plat/arm/sgi): add CPU specific handler for Neoverse N2

The 'CORE_PWRDN_EN' bit of 'CPUPWRCTLR_EL1' register requires an
explicit write to clear it for hotplug and idle to function correctly.
So add Neoverse N2 CPU specific handler in platform reset handler to
clear the CORE_PWRDN_EN bit.

Signed-off-by: shriram.k <shriram.k@arm.com>
Change-Id: If3859447410c4b8e704588993941178fa9411f52
1 file changed