drm/msm/dp: reallocate EDID buffer when needed

In certain cases the pre-allocated EDID buffer is not
enough for incoming EDID data, so reallocate the buffer
according to the actual EDID data size.

CRs-Fixed: 2291153
Change-Id: I9960758dc405757c8ca07e2cbdcdcdad91a9b045
Signed-off-by: Ray Zhang <rayz@codeaurora.org>