ARM: omap: remove references to disable_irq_lch

The disable_irq_lch method is never actually used, so there's not much
point it existing; remove it.

Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-omap1/dma.c

@@ -363,7 +363,6 @@ static int __init omap1_system_dma_init(void)
 	p->clear_dma		= omap1_clear_dma;
 	p->dma_write		= dma_write;
 	p->dma_read		= dma_read;
-	p->disable_irq_lch	= NULL;
 
 	p->errata = configure_dma_errata();