MdePkg: Correct condition check for AcpiExp text format

MdePkg: Correct condition check for AcpiExp text format

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1226

According to UEFI Spec, for ACPI Expanded Device Path,
when HIDSTR=empty, CIDSTR=empty, UID STR!=empty,
the ACPI Expanded Device Path node can be displayed as
AcpiExp(HID,CID,UIDSTR) format.
And if UID is 0 and UIDSTR is empty, then use AcpiEx format.

This patch is to correct the condition check to follow UEFI
Spec when convert the device path node to the AcpiExp text
format.

Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>