[POWERPC] 83xx: Correct 2nd PCI controller interrupt value in mpc834x_mds dts

According to the 8349EA ref man, the second PCI PHB IRQ is 67.  Thanks to Peter
Van Ackeren for finding this.

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>