ddraw/tests: Rename mips to mipmaps

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
https://testbot.winehq.org/JobDetails.pl?Key=18975

Your paranoid android.


=== w1064 (32 bit dsurface) ===
dsurface.c:296: Test failed: Destination data after blitting is not correct
dsurface.c:330: Test failed: Destination data after blitting is not correct
dsurface.c:509: Test failed: Surface data after srckey blit does not match
dsurface.c:534: Test failed: Surface data after src override key blit does not match
dsurface.c:588: Test failed: Surface data after dest key blit does not match
dsurface.c:614: Test failed: Surface data after dest key override blit does not match
dsurface.c:676: Test failed: Surface data with src key and dest key blit does not match