[U-Boot] [U-Boot, v2] efi_selftest: check for buffer overflow in efi_get_variable

[Alexander Graf]

> Allocate a buffer on the stack instead of an array of uninitialized
> pointers; check if GetVariable writes past the end of the buffer.
> 
> Signed-off-by: Ivan Gorinov <ivan.gorinov at intel.com>

Thanks, applied to efi-next

Alex