drm/msm: correct GPL V2.0 license for display driver files

In commit 1eae18f0 ("drm/msm: Add snapshot of SDE, DSI,
DP and supporting files") GPL V2.0 licensing information is
duplicated at the beginning of the file. This
change corrects these files.

Change-Id: I4c8db5520f76d6e05c2e80a2385be5c71858136f
Signed-off-by: Samantha Tran <samtran@codeaurora.org>