drm/armada: Use drm_fb_helper_fill_info

Only changes the name of the fb from "armada-drmfb" to armadadrmfb.

v2: Rebase

v3: Fix commit message (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: Russell King <linux@armlinux.org.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190326132008.11781-5-daniel.vetter@ffwll.ch