disp: msm: dp: fix test pattern selection

Use one level lower test pattern in case the current
test pattern fails to train link. This helps with few
monitors which sometimes fail with a selected test
pattern. Instead of failing the link, try with a lower
test pattern.

CRs-Fixed: 2507729
Change-Id: I394253398f49b03084dc547dacaededa49a9c527
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>