arm64: dts: broadcom: bcm4908: Fix timer node for BCM4906 SoC

arm64: dts: broadcom: bcm4908: Fix timer node for BCM4906 SoC

BugLink: https://bugs.launchpad.net/bugs/1988351
[ Upstream commit b4a544e415e9be33b37d9bfa9d9f9f4d13f553d6 ]

The cpu mask value in interrupt property inherits from bcm4908.dtsi
which sets to four cpus. Correct the value to two cpus for dual core
BCM4906 SoC.

Fixes: c8b404fb05dc ("arm64: dts: broadcom: bcm4908: add BCM4906 Netgear R8000P DTS files")
Signed-off-by: William Zhang <william.zhang@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>