efi_loader: define internal implementations of install/uninstallmultiple

A following patch is cleaning up the core EFI code trying to remove
sequences of efi_create_handle, efi_add_protocol.

Although this works fine there's a problem with the latter since it is
usually combined with efi_delete_handle() which blindly removes all
protocols on a handle and deletes the handle.  We should try to adhere to
the EFI spec which only deletes a handle if the last instance of a protocol
has been removed.  Another problem is that efi_delete_handle() never checks
for opened protocols,  but the EFI spec defines that the caller is
responsible for ensuring that there are no references to a protocol
interface that is going to be removed.

So let's fix this by replacing all callsites of
efi_create_handle(), efi_add_protocol() , efi_delete_handle() with
Install/UninstallMultipleProtocol.

In order to do that redefine functions that can be used by the U-Boot
proper internally and add '_ext' variants that will be used from the
EFI API

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>