drm/msm/dpu: fix documentation for intf_type

Fix intf_type description in msm_disp_info to show that
it represents drm encoder mode of the display.

changes in v3:
	- introduced in the series
changes in v4:
	- none

Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>