efi_loader: DisconnectController() with no driver

If DisconnectController() is called and no driver is managing
ControllerHandle, return EFI_SUCCESS.

UEFI SCT II 2017, 3.3.12 DisconnectController(), 5.1.3.12.4 - 5.1.3.12.6

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