efi_loader: simplify efi_remove_all_protocols

Replace list_for_each_safe() and list_entry() by
list_for_each_entry_safe().

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Alexander Graf <agraf@suse.de>