drm/msm/dsi: use correct enum in dsi_get_cmd_fmt

[ Upstream commit a4af89286f8fc382459308764ea05935dc477cdc ]

The function dsi_get_cmd_fmt returns enum dsi_cmd_dst_format,
use the correct enum value also for MIPI_DSI_FMT_RGB666/_PACKED.

This has been discovered using clang:
  drivers/gpu/drm/msm/dsi/dsi_host.c:743:35: warning: implicit conversion
        from enumeration type 'enum dsi_vid_dst_format' to different
        enumeration type 'enum dsi_cmd_dst_format' [-Wenum-conversion]
          case MIPI_DSI_FMT_RGB666:       return VID_DST_FORMAT_RGB666;
                                          ~~~~~~ ^~~~~~~~~~~~~~~~~~~~~.

Change-Id: I0dddb33add814e8815dac10dbf6ae6b50bcc6418
Signed-off-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Git-repo: https://source.codeaurora.org/quic/la/kernel/msm-4.4


Git-commit: 5151a0c8d730509cc92ac2d1a2697dd0fe48be59
Signed-off-by: Swetha Chikkaboraiah <schikk@codeaurora.org>