ARM: OMAP2+: INTC: fix Kconfig option for TI81XX

The INTC core is using a Kconfig option for TI816x which doesn't
exist.  Convert it to use TI81XX.

Cc: Hemant Pedanekar <hemantp@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>
Acked-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>