efi: Correct display of table GUIDs

The printf() %pU option decodes GUIDs so it is not necessary to do this
first. Drop the incorrect code.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>