drm/tilcdc: Remove tilcdc_crtc_max_width(), use private data

We already have a private data member for maximum display width so
let's use it and get rid of the redundant tilcdc_crtc_max_width().

The LCDC version probing is moved to before reading the device tree
properties so that the version information is available when private
data maximum width is initialized, if "max-width" property is not
found.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/73683d2ce151cffb811a756595b02892eeac3d84.1602349100.git.jsarha@ti.com