MdeModulePkg/DxePrintLibPrint2Protocol: make mStatusString array CONST

Change the type of mStatusString[] to reflect that it is a CONST
array of pointers to CONST.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18022 6f19259b-4bc3-4df7-8a09-765794883524