OvmfPkg: Add 4K PE alignment to enable SMM page level protection.

OvmfPkg: Add 4K PE alignment to enable SMM page level protection.

Tested boot with below configuration:
IA32
IA32X64
X64

Tested boot with XD enabled/disabled.

Requested-by: Laszlo Ersek <lersek@redhat.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>