OvmfPkg: make sure ResetCold() and ResetWarm() never return

OvmfPkg: make sure ResetCold() and ResetWarm() never return

Also, add a small delay after the 0xCF9 hard reset request -- on qemu/kvm the
port access is translated to the qemu-internal system reset request by the CPU
thread, and it might progress some more before the IO thread acts upon the
system reset request.

MicroSecondDelay() is implemented by OvmfPkg's own AcpiTimerLib.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@14158 6f19259b-4bc3-4df7-8a09-765794883524