ARM: dts: cygnus: fix irq type for arm global timer

As per ARM documentation
PPI(0) ID27 - global timer interrupt is rising-edge sensitive.

set IRQ triggering type to IRQ_TYPE_EDGE_RISING for ARM Global timers.

Fixes: c9ad7bc5

 ("ARM: dts: Enable Broadcom Cygnus SoC")
Signed-off-by: Clément Péron <peron.clem@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>