efi_selftest: Remove loadfile2 for initrd selftests

We are redefining how u-boot locates the initrd to load via the kernel
LoadFile2 protocol.  This selftest is not relevant any more, so remove
it. A new one will be added later

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