Add DEPEX on gEdkiiFormBrowserEx2ProtocolGuid to BootMenu (#138)

## Description
BootMenu should have a DEPEX on gEdkiiFormBrowserEx2ProtocolGuid and
should not return failure (to avoid unloading the driver after creating
events and installing protocol interfaces).

- [x] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [ ] Impacts security?
- **Security** - Does the change have a direct security impact on an
application,
    flow, or firmware?
  - Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
- [ ] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
    in build or boot behavior?
- Examples: Add a new library class, move a module to a different repo,
call
    a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
- **Documentation** - Does the change contain explicit documentation
additions
    outside direct code modifications (and comments)?
- Examples: Update readme file, add feature readme file, link to
documentation
    on an a separate Web page, ...

## How This Was Tested

Tested on Q35

## Integration Instructions

N/A

OemPkg/BootMenu/BootMenu.c

@@ -550,13 +550,12 @@ BootMenuEntry (
                                  );
   if (mBootMenuPrivate.HiiHandle == NULL) {
     DEBUG ((DEBUG_ERROR, "%a: Error on HiiAddPackages. Code=%r\n", __FUNCTION__, Status));
-
-    return EFI_OUT_OF_RESOURCES;
+  } else {
+    Status = gBS->LocateProtocol (&gEdkiiFormBrowserEx2ProtocolGuid, NULL, (VOID **)&mBrowserEx2);
+    ASSERT_EFI_ERROR (Status);
   }
 
-  Status = gBS->LocateProtocol (&gEdkiiFormBrowserEx2ProtocolGuid, NULL, (VOID **)&mBrowserEx2);
-
-  return Status;
+  return EFI_SUCCESS;
 }
 
 /**

OemPkg/BootMenu/BootMenu.inf

@@ -68,4 +68,4 @@
 [Pcd]
 
 [Depex]
-  TRUE
+  gEdkiiFormBrowserEx2ProtocolGuid