OMAP: DSS2: Have separate irq handlers for DISPC and DSI

Currently, the core DSS platform device requests for an irq line for OMAP2 and
OMAP3. Make DISPC and DSI platform devices request for a shared IRQ line.

On OMAP3, the logical OR of DSI and DISPC interrupt lines goes to the MPU. There
is a register DSS_IRQSTATUS which tells if the interrupt came from DISPC or DSI.

On OMAP2, there is no DSI, only DISPC interrupts goto the MPU. There is no
DSS_IRQSTATUS register.

Hence, it makes more sense to have separate irq handlers corresponding to the
DSS sub modules instead of having a common handler.

Since on OMAP3 the logical OR of the lines goes to MPU, the irq line is shared
among the IRQ handlers.

The hwmod irq info has been removed for DSS to DISPC and DSI for OMAP2 and OMAP3
hwmod databases. The Probes of DISPC and DSI now request for irq handlers.

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