IntelFrameworkModulePkg/Csm: Set CSM memory executable

IntelFrameworkModulePkg/Csm: Set CSM memory executable

Commit b22a62be5cdc8fd19d87ec1ecfa5b28fb9be50ad
* IntelFrameworkModule/LegacyBios:Use reserved memory for legacy data
allocates reserved memory for holding legacy code/data.

But with PcdDxeNxMemoryProtectionPolicy set to certain value to
forbid execution when code is in certain type of memory, it's
possible that a platform forbids execution when code is in reserved
memory. The patch calls GCD service to allow such case otherwise
CPU exception may occur.

Code execution in BSCode area should be enabled by platform by
default.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jian Wang <jian.j.wang@intel.com>