MIPS: SEAD-3: Remove GIC timer from DT

MIPS: SEAD-3: Remove GIC timer from DT

The SEAD-3 board doesn't & never has configured the GIC frequency.
Remove the timer node from the DT in order to avoid attempting to probe
the GIC clocksource/clockevent driver which will produce error messages
such as these during boot:

[    0.000000] GIC frequency not specified.
[    0.000000] Failed to initialize '/interrupt-controller@1b1c0000/timer': -22
[    0.000000] clocksource_probe: no matching clocksources found

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16188/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>