arm64: dts: ls1028a: sl28: re-enable ftm_alarm0

Commit dd3d936a ("arm64: dts: ls1028a: add ftm_alarm1 node to be
used as wakeup source") disables ftm_alarm0 in the SoC dtsi but doesn't
enable it on the board which is still using it. Re-enable it on the sl28
board.

Fixes: dd3d936a ("arm64: dts: ls1028a: add ftm_alarm1 node to be used as wakeup source")
Reported-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>