omap1: DMA: move LCD related code from plat-omap to mach-omap1

All of the LCD DMA code in plat-omap/dma.c appears to be OMAP1-only (and
apparently only is available on a subset of OMAP1 chips).

Move this code to mach-omap1/lcd_dma.c.

Tested on OMAP1510 Amstrad Delta.
Compile-tested with omap_generic_2420_defconfig.

Reported-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Reviewed-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>