arm64: dts: ls1028a: add ftm_alarm1 node to be used as wakeup source

Add flextimer2 based ftm_alarm1 node and enable it to be the default rtc
wakeup source for rdb and qds boards instead of the original flextimer1
which is used by PWM.  The ftm_alarm0 node hence is disabled by default.

Signed-off-by: Biwen Li <biwen.li@nxp.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>