board: ti: am57xx-idk: Auto detect LCD Panel

AM571x IDK and AM572x IDK have optional LCD Kits that can be purchased.
These can be one of OSD101T2045 or the newer OSD101T2587. The LCD panel
itself has no registers that can be used to identify the panel, however,
the touchscreen controllers on the panels are different.

Hence to ease user experience, we can use the touch screen controller's
ID information to detect what kind of panel we use and select the
appropriate kernel dtb for the platform configuration.

NOTE: AM572x IDK default configuration is for LCD Connectivity, however
the AM571x IDK has a jumper (J51) that needs to be mounted for the IDK
to operate with LCD (Vs two PRUSS ethernet port option).

Touchscreen ID information is documented in:
http://www.osddisplays.com/TI/OSD101T2587-53TS_A.1.pdf



Acked-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>