MdeModulePkg Ps2KbDxe: Execute key notify func at TPL_CALLBACK

Current implementation executes key notify function in TimerHandler
at TPL_NOTIFY. The code change is to make key notify function
executed at TPL_CALLBACK to reduce the time occupied at TPL_NOTIFY.

The code will signal KeyNotify process event if the key pressed
matches any key registered and insert the KeyData to the EFI Key
queue for notify, then the KeyNotify process handler will invoke
key notify functions at TPL_CALLBACK.

Cc: Ruiyu Ni <Ruiyu.ni@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Ruiyu Ni <Ruiyu.ni@intel.com>

MdeModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2Keyboard.h

@@ -105,6 +105,7 @@ typedef struct {
   //
   SCAN_CODE_QUEUE                     ScancodeQueue;
   EFI_KEY_QUEUE                       EfiKeyQueue;
+  EFI_KEY_QUEUE                       EfiKeyQueueForNotify;
 
   //
   // Error state
@@ -118,6 +119,7 @@ typedef struct {
   // Notification Function List
   //
   LIST_ENTRY                          NotifyList;
+  EFI_EVENT                           KeyNotifyProcessEvent;
 } KEYBOARD_CONSOLE_IN_DEV;
 
 #define KEYBOARD_CONSOLE_IN_DEV_FROM_THIS(a)  CR (a, KEYBOARD_CONSOLE_IN_DEV, ConIn, KEYBOARD_CONSOLE_IN_DEV_SIGNATURE)
@@ -268,6 +270,19 @@ KeyGetchar (
   IN OUT KEYBOARD_CONSOLE_IN_DEV *ConsoleIn
   );
 
+/**
+  Process key notify.
+
+  @param  Event                 Indicates the event that invoke this function.
+  @param  Context               Indicates the calling context.
+**/
+VOID
+EFIAPI
+KeyNotifyProcessHandler (
+  IN  EFI_EVENT                 Event,
+  IN  VOID                      *Context
+  );
+
 /**
   Perform 8042 controller and keyboard Initialization.
   If ExtendedVerification is TRUE, do additional test for