MdePkg: Remove FIT table industry standard header file.

MdePkg: Remove FIT table industry standard header file.

Commit c7c964b and dd01704 add header file for FIT table and update
MpInitLib to support FIT based microcode shadow operation. There are
comments that FIT is Intel specific specification instead of industry
standard, which should not be placed in EDK2 MdePkg and UefiCpuPkg.
This patch removes the header file added by c7c964b.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Siyuan Fu <siyuan.fu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>