ARM: dts: UniPhier: fix PPI interrupt CPU mask of timer nodes

This SoC is integrated with 4 Cortex-A9 cores.  The GIC bindings
document says that the bits[15:8] of the 3rd cell of the interrupts
property represents PPI interrupt CPU mask.  Because the timer
interrupts are wired to all of the 4 cores, bits[15:8] should be set
to 0xf.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Olof Johansson <olof@lixom.net>