drm/msm/dpu: Remove unnecessary NULL check

dpu_encoder_virt.phys_encs[0:num_phys_encs-1] will not be NULL so don't
check.

Also fix multiline strings that caused checkpatch warning.

Signed-off-by: Drew Davenport <ddavenport@chromium.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>