OvmfPkg: Make more use of ARRAY_SIZE()

OvmfPkg: Make more use of ARRAY_SIZE()

Convert the remaining pieces to make the code shorter and more readable.

Cc: Justen Jordan <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
[lersek@redhat.com: tweak subject line]
Signed-off-by: Laszlo Ersek <lersek@redhat.com>