StandaloneMmPkg: Fix few typos

Fix few typos in comments.

Cc: Achin Gupta <achin.gupta@arm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Supreeth Venkatesh <supreeth.venkatesh@arm.com>
Signed-off-by: Antoine Coeur <coeur@gmx.fr>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Philippe Mathieu-Daude <philmd@redhat.com>
Message-Id: <20200207010831.9046-76-philmd@redhat.com>

StandaloneMmPkg/Core/Dependency.c

@@ -372,7 +372,7 @@ MmIsSchedulable (
     // The math is done out of order, but it should not matter. That is
     // we may add in the sizeof (EFI_GUID) before we account for the OP Code.
     // This is not an issue, since we just need the correct end result. You
-    // need to be careful using Iterator in the loop as it's intermediate value
+    // need to be careful using Iterator in the loop as its intermediate value
     // may be strange.
     //
     Iterator++;

StandaloneMmPkg/Core/FwVol.c

@@ -50,7 +50,7 @@ MmCoreFfsFindMmDriver (
 
 Routine Description:
   Given the pointer to the Firmware Volume Header find the
-  MM driver and return it's PE32 image.
+  MM driver and return its PE32 image.
 
 Arguments:
   FwVolHeader - Pointer to memory mapped FV

StandaloneMmPkg/Core/StandaloneMmCore.c

@@ -354,7 +354,7 @@ MmEntryPoint (
   //PlatformHookBeforeMmDispatch ();
 
   //
-  // If a legacy boot has occured, then make sure gMmCorePrivate is not accessed
+  // If a legacy boot has occurred, then make sure gMmCorePrivate is not accessed
   //
 
   //

StandaloneMmPkg/Library/StandaloneMmPeCoffExtraActionLib/StandaloneMmPeCoffExtraActionLib.inf

@@ -1,5 +1,5 @@
 #/** @file
-# PeCoff extra action libary for DXE phase that run Unix emulator.
+# PeCoff extra action library for DXE phase that run Unix emulator.
 #
 # Lib to provide memory journal status code reporting Routines
 # Copyright (c) 2007 - 2010, Intel Corporation. All rights reserved.<BR>