MdeModulePkg CapsuleApp: Do not parse bits in CapsuleFlags of ESRT

MdeModulePkg CapsuleApp: Do not parse bits in CapsuleFlags of ESRT

According to UEFI spec, only bits 0-15 of CapsuleFlags are
meaningful and CapsuleGuid specific, CAPSULE_FLAGS_PERSIST_ACROSS_RESET
CAPSULE_FLAGS_POPULATE_SYSTEM_TABLE/CAPSULE_FLAGS_INITIATE_RESET
defined in UEFI spec are in bits 16-31, they should not be parsed in
CapsuleFlags of ESRT.

CapsuleFlags
The capsule flags field contains the CapsuleGuid flags (bits 0-15)
as defined in the EFI_CAPSULE_HEADER that will be set in the capsule
header.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>