tests: Use printf instead of debug_printf in u_format_compatible_test.

tests: Use printf instead of debug_printf in u_format_compatible_test.

Use printf instead of debug_printf to be consistent with print
statements in rest of unit tests.

This also fixes the lack of print output with the MinGW build of
u_format_compatible_test.

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Brian Paul <brianp@vmware.com>