OMAPDSS: ls037v7dw01: remove platform backlight calls

Sharp ls037v7dw01 driver contains support to call platform backlight
functions. These are not used by any board, and can be removed.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Archit Taneja <archit@ti.com>