efidebug: defaults prints incorrect hardcoded path to executable

[Filip Žaludek]

Hello,

path to efi executable can be re-defined in..
https://github.com/u-boot/u-boot/blob/master/boot/bootmeth_efi.c#L26

but then 'efidebug defaults' prints incorrect hardcoded path..
https://github.com/u-boot/u-boot/blob/master/cmd/efidebug.c#L529


I am not advocating any circumvention of uefi std boot flows, but anticipating EFI_DIRNAME definition as close as 
possible to BOOTEFI_NAME.
Perhaps in header file?

Not touching any code. Regards!
Filip