OMAPDSS: DISPC: Add IRQ enable/status helpers

DISPC irqs need to be handled from the compat layer and also in the
future by the omapdrm. To make this possible, this patchs adds a set of
helper functions, so that the irqs can be managed without direct
register reads/writes.

The following functions are added, and all the current direct reg
reads/writes are changed to use these.

u32 dispc_read_irqstatus(void);
void dispc_clear_irqstatus(u32 mask);
u32 dispc_read_irqenable(void);
void dispc_write_irqenable(u32 mask);

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
diff --git a/drivers/video/omap2/dss/dss.h b/drivers/video/omap2/dss/dss.h
index e3e5a63..d614fda 100644
--- a/drivers/video/omap2/dss/dss.h
+++ b/drivers/video/omap2/dss/dss.h
@@ -397,6 +397,10 @@
 int dispc_init_platform_driver(void) __init;
 void dispc_uninit_platform_driver(void) __exit;
 void dispc_dump_clocks(struct seq_file *s);
+u32 dispc_read_irqstatus(void);
+void dispc_clear_irqstatus(u32 mask);
+u32 dispc_read_irqenable(void);
+void dispc_write_irqenable(u32 mask);
 
 int dispc_runtime_get(void);
 void dispc_runtime_put(void);