Add LINUX_EFI_INITRD_MEDIA_GUID to our collection of GUID definitions, it can be used in a media device path to specify a Linux style initrd that can be loaded by the OS using the LoadFile2 protocol. Move these defines to MdePkg from OvmfPkg as these are relevant to non-OVMF targets as well. Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2564 Signed-off-by: Jeff Brasen <jbrasen@nvidia.com> Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com> Acked-by: Ard Biesheuvel <ardb@kernel.org>