SecurityPkg SecureBootConfigDxe: Add check for the external PE/COFF image.

SecurityPkg SecureBootConfigDxe: Add check for the external PE/COFF image.

Use BasePeCoffLib PeCoffLoaderGetImageInfo() to check the PE/COFF image.

In V2, add specific ImageRead() to make sure the PE/COFF image content
read is within the image buffer.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Chao Zhang <chao.b.zhang@intel.com>