msm_fb: display: Move debug messages to debug statistics

Move some debug messages that were shown as errors in display driver
to debug statistics to avoid excesive prints in kernel log.

CRs-Fixed: 326925
Change-Id: I529586f0e79baf27e2ae17f08fac203ba28bf416
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>