libefivar: Support UefiDevicePathLib under StandaloneMm

This change added an instance of UefiDevicePathLib for StandaloneMm. It
abstracts DevicePathFromHandle function into different files for
Standalone MM and other instances to avoid linking gBS into MM_STANDALONE
drivers.

No functional change intended, as this function and its invocation are ifdefd
out.

Obtained from:	https://github.com/tianocore/edk2/commit/14a746bb6a92d59669c67a970479558734cf2383

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/1894

lib/libefivar/uefi-dputil.c

@@ -856,39 +856,6 @@ UefiDevicePathLibIsDevicePathMultiInstance (
 }
 
 
-/**
-  Retrieves the device path protocol from a handle.
-
-  This function returns the device path protocol from the handle specified by Handle.
-  If Handle is NULL or Handle does not contain a device path protocol, then NULL
-  is returned.
-
-  @param  Handle                     The handle from which to retrieve the device
-                                     path protocol.
-
-  @return The device path protocol from the handle specified by Handle.
-
-**/
-EFI_DEVICE_PATH_PROTOCOL *
-EFIAPI
-DevicePathFromHandle (
-  IN EFI_HANDLE                      Handle
-  )
-{
-  EFI_DEVICE_PATH_PROTOCOL  *DevicePath;
-  EFI_STATUS                Status;
-
-  Status = gBS->HandleProtocol (
-                  Handle,
-                  &gEfiDevicePathProtocolGuid,
-                  (VOID *) &DevicePath
-                  );
-  if (EFI_ERROR (Status)) {
-    DevicePath = NULL;
-  }
-  return DevicePath;
-}
-
 /**
   Allocates a device path for a file and appends it to an existing device path.