efi_loader: don't use EFI_LOADER_DATA internally

EFI_LOADER_DATA/CODE is reserved for EFI applications.
Memory allocated by U-Boot for internal usage should be
EFI_BOOT_SERVICES_DATA or _CODE or EFI_RUNTIME_SERVICES_DATA or _CODE.

Reported-by: François-Frédéric Ozog <ff@ozog.com>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: François-Frédéric Ozog <ff@ozog.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>