arm: davinci: Use generic irq chip

Simple conversion which simply uses the fact that the second irq chip
base address has offset 0x04 to the first one.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-and-Tested-by: Kevin Hilman <khilman@ti.com>
Tested-by: Sekhar Nori <nsekhar@ti.com>