MdeModulePkg: Make boot option description unique

MdeModulePkg: Make boot option description unique

When there are multiple network boot options, user will see multiple
"UEFI Network" boot options. It's hard to distinguish them using the
description.
The patch enhances the boot option generation logic to append " 2"
/" 3"/" 4"/... number suffix to the non-first network boot options.
So the 2nd one becomes "UEFI Network 2".

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18062 6f19259b-4bc3-4df7-8a09-765794883524