ArmPkg: allow HYP timer interrupt to be omitted

ArmPkg: allow HYP timer interrupt to be omitted

The DT binding for the ARM generic timer describes the secure,
non-secure, virtual and hypervisor timer interrupts, respectively.
However, under virtualization, only the virtual timer is usable, and
the device tree may omit the hypervisor timer interrupt. (Other timer
interrupts cannot be omitted simply due to the fact that the virtual
timer is listed third)

Contributed-under: TianoCore Contribution Agreement 1.0
Reviewed-by: Olivier Martin <olivier.martin@arm.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16953 6f19259b-4bc3-4df7-8a09-765794883524