omap1: LCD_DMA: Use some define rather than a hexadecimal

The patch corrects the issue introduced with one of my earlier patches:
	OMAP: DMA: Fix omapfb/lcdc on OMAP1510 broken when PM set[1]
as pointed out by OMAP subsystem maintainer.

Applies on top of my prevoius patch:
  OMAP: DMA: move LCD DMA related code from plat-omap to mach-omap1[2]

Tested on Amstrad Delta
Compile tested with omap_generic_2420_defconfig

[1] http://patchwork.kernel.org/patch/57922/
[2] http://patchwork.kernel.org/patch/61952/

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Signed-off-by: Tony Lindgren <tony@atomide.com>