ShellPkg/UefiShellAcpiViewCommandLib: Fix ECC issues

1. Separate variable definition and initialization.
2. Make the variable naming following Edk2 rule.

V2: Remove the updates of guard macros in header files.

Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Evan Lloyd <evan.lloyd@arm.com>
Cc: Jaben Carsey <jaben.carsey@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>

ShellPkg/Library/UefiShellAcpiViewCommandLib/UefiShellAcpiViewCommandLib.c

@@ -64,7 +64,10 @@ RegisterAllParsers (
   )
 {
   EFI_STATUS Status;
-  UINTN Count = sizeof (ParserList) / sizeof (ParserList[0]);
+  UINTN Count;
+
+  Count = sizeof (ParserList) / sizeof (ParserList[0]);
+
   while (Count-- != 0) {
     Status = RegisterParser (
                ParserList[Count].Signature,