irqchip: omap-intc: Fix legacy DMA regression

commit 55601c9f (arm: omap: intc: switch over
to linear irq domain) introduced a regression with
SDMA legacy driver because that driver strictly depends
on INTC's IRQs starting at NR_IRQs. Aparently
irq_domain_add_linear() won't guarantee that, since we see
a 7 IRQs difference when booting with and without the
commit cited above.

Until arch/arm/plat-omap/dma.c is properly fixed, we
must maintain OMAP2/3 using irq_domain_add_legacy().

A FIXME note was added so people know to delete that
code once that legacy DMA driver is fixed up.

Fixes: 55601c9f (arm: omap: intc: switch over to linear irq domain)
Cc: <stable@vger.kernel.org> # v3.18
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Tested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Link: https://lkml.kernel.org/r/1420576688-10604-1-git-send-email-balbi@ti.com


Signed-off-by: Jason Cooper <jason@lakedaemon.net>