MdeModulePkg/Esrt: Add ESRT_FW_TYPE_SYSTEMFIRMWARE check.

The previous ESRT driver unconditionally treat FMP to be
ESRT_FW_TYPE_DEVICEFIRMWARE.
EDKII System Capsule reuses FMP, but it is ESRT_FW_TYPE_SYSTEMFIRMWARE.

Add check to ImageTypeId check to see if it is ESRT_FW_TYPE_SYSTEMFIRMWARE.

Cc: Feng Tian <feng.tian@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Chao Zhang <chao.b.zhang@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>
Tested-by: Michael Kinney <michael.d.kinney@intel.com>