ovmf: fix gcc12 warning for device path handling

Backport [https://github.com/tianocore/edk2/commit/22130dcd98b4d4b76ac8d922adb4a2dbc86fa52c

]

Fixes:

In function ?SetDevicePathEndNode?,
    inlined from ?FileDevicePath? at DevicePathUtilities.c:857:5:
DevicePathUtilities.c:321:3: error: writing 4 bytes into a region of size 1 [-Werror=stringop-overflow=]
  321 |   memcpy (Node, &mUefiDevicePathLibEndDevicePath, sizeof (mUefiDevicePathLibEndDevicePath));
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from UefiDevicePathLib.h:22,
                 from DevicePathUtilities.c:16:
../Include/Protocol/DevicePath.h: In function ?FileDevicePath?:
../Include/Protocol/DevicePath.h:51:9: note: destination object ?Type? of size 1
   51 |   UINT8 Type;       ///< 0x01 Hardware Device Path.
      |         ^~~~

Signed-off-by: Steve Sakoman <steve@sakoman.com>