StdLib/LibC/StdLib/Malloc.c: Revert cast removal to fix GCC build breakage.

StdLib/LibC/StdLib/Malloc.c: Revert cast removal to fix GCC build breakage.

The cast to (void**) is needed for the last parameter of the AllocatePool call in malloc().  This is because type CPOOL_HEAD** is not automatically promoted to void**, as required by AllocatePool().

This was originally addressed in SVN revision 15474 but removed again in 15664.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Daryl McDaniel <daryl.mcdaniel@intel.com>
Reviewed by: Stefan Kaeser <stefankaeser@hotmail.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15677 6f19259b-4bc3-4df7-8a09-765794883524