bdinfo: Correct use of assertions

bdinfo: Correct use of assertions

This test was written for the incorrect use of assertions. Update it to
build with the previous approach, where tests fail at the first
assertion.

All assertion functions return 0 on success and non-zero on failure.
They can be nested into functions simply by declaring a function that
returns an int and using ut_assertok() to call it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Marek Vasut <marex@denx.de>