drm/msm: Use drm_fb_helper_fill_info

This will change the fb name from "msm" to "msmdrmfb".

v2: Rebase

v3: Fix subject prefix (Noralf)

Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: linux-arm-msm@vger.kernel.org
Cc: freedreno@lists.freedesktop.org
Link: https://patchwork.freedesktop.org/patch/msgid/20190326132008.11781-13-daniel.vetter@ffwll.ch