efi_loader: replace printf by log in efi_uclass.c

Use logging functions instead of printf() and debug().

Change logging messages for uclass creation and destruction to log_debug().

Reported-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>