OvmfPkg: provide a generic implementation of QemuLoadImageLib

Implement QemuLoadImageLib, and make it load the image provided by the
QEMU_EFI_LOADER_FS_MEDIA_GUID/kernel device path that we implemented
in a preceding patch in a separate DXE driver, using only the standard
LoadImage and StartImage boot services.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2566
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf

@@ -0,0 +1,38 @@
+## @file
+#  Generic implementation of QemuLoadImageLib library class interface.
+#
+#  Copyright (c) 2020, ARM Ltd. All rights reserved.<BR>
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 1.27
+  BASE_NAME                      = GenericQemuLoadImageLib
+  FILE_GUID                      = 9e3e28da-c7b5-4f85-841a-84e6a9a1f1a0
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = QemuLoadImageLib|DXE_DRIVER
+
+[Sources]
+  GenericQemuLoadImageLib.c
+
+[Packages]
+  MdeModulePkg/MdeModulePkg.dec
+  MdePkg/MdePkg.dec
+  OvmfPkg/OvmfPkg.dec
+
+[LibraryClasses]
+  DebugLib
+  MemoryAllocationLib
+  PrintLib
+  QemuFwCfgLib
+  UefiBootServicesTableLib
+
+[Protocols]
+  gEfiDevicePathProtocolGuid
+  gEfiLoadedImageProtocolGuid
+
+[Guids]
+  gQemuKernelLoaderFsMediaGuid