efi_loader: EFI_UNACCEPTED_MEMORY_TYPE

* UEFI spec 2.9 introduced a new memory type EFI_UNACCEPTED_MEMORY_TYPE.
  Add it to enum EFI_MEMORY_TYPE.
* Add missing EFI_MEMORY_CPU_CRYPTO constant
* Improve description of EFI_PERSISTENT_MEMORY_TYPE

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>