[PATCH,v2] efi: make EFI a menuconfig to ease disabling it all

[Vincent Legoll]

The following v2 patch adds the "default y" to avoid breaking existing
configs.

I don't know if using the CONFIG_EFI symbol would be better, it is spread
in multiple arch/*/Kconfig files, and would make the changes more invasive.

Please advise the way forward

Thanks