serial console on upsquared board does not work

Close for JJ RC1

Resolved by:

https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/24469

I've narrowed the kernel configuration options down that get it working again, suspect it would take some digging to work out why things worked previously without them.  I'll upload a fix today.

Just to note, serial works on minnow with qemu image

, I believe it's not that.  The serial port for the console on the up^2 is ttyS0, and I had previously added a "_remove" to remove the extra ttyS2 for intel-corei7-64 to quiet systemd complaining it did not exist.  When I check with "bitbake -e", SERIAL_CONSOLES is "115200;ttyS0 115200;ttyS1", which should work, and I believe did with zeus.  My current theory is this is stemming from a kernel configuration/behavior change.  I noticed yesterday that we never added all the extra kernel configuration done for minnow/up^2 hardware into the qemu kernel, my suspicion is that's making a difference now for some reason (ACPI, perhaps).  I tried with a couple of likely candidate options yesterday. but no luck yet.