NetworkPkg: Remove a CopyMem to speed up the HTTP boot download.

NetworkPkg: Remove a CopyMem to speed up the HTTP boot download.

This patch updates the HTTP boot driver to use the caller provided buffer
directly in identity transfer-coding mode, this could save one time CopyMem
operation to benefit the download performance.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Zhang Lubo <lubo.zhang@intel.com>
Reviewed-by: Jiaxin Wu <jiaxin.wu@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19482 6f19259b-4bc3-4df7-8a09-765794883524