ShellPkg: Comments update and code refine.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qiu Shumin <shumin.qiu@intel.com>
Reviewed-by: Jaben Carsey <Jaben.carsey@intel.com>
Reviewed-by: Erik Bjorge <erik.c.bjorge@intel.com>


git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16209 6f19259b-4bc3-4df7-8a09-765794883524
Removes dead code from the PlatformBdsLibNull,leaving this unused code might confuse the user.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <olivier.martin@arm.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>


git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16210 6f19259b-4bc3-4df7-8a09-765794883524
MdeModulePkg PeiCore: Update the code of PeiAllocatePages() to correctly consider the overhead sizeof (EFI_HOB_MEMORY_ALLOCATION).

It can fix the confused ERROR log like below.

"AllocatePages failed: No 0x1 Pages is available.
There is only left 0x1 pages memory resource to be allocated."

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16211 6f19259b-4bc3-4df7-8a09-765794883524