FmpDevicePkg/FmpDxe: Remove use of CatSprint()

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1525

The size overhead for CatSPrint() is large.  This function
is only used to generate variable names with HardwareInstance
value appended.  Use UnicodeValueToStringS() instead that is
much smaller.

Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Eric Jin <eric.jin@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

FmpDevicePkg/FmpDxe/FmpDxe.h

@@ -23,6 +23,7 @@
 #include <Library/UefiRuntimeServicesTableLib.h>
 #include <Library/MemoryAllocationLib.h>
 #include <Library/UefiLib.h>
+#include <Library/PrintLib.h>
 #include <Library/FmpAuthenticationLib.h>
 #include <Library/FmpDeviceLib.h>
 #include <Library/FmpPayloadHeaderLib.h>