AGL not booting up in imx8mq-evk board when build using octopus and master branch

Close for OO 15.0.3

Since Gerrit integration seems to be not working post-JIRA upgrade, for reference the change is:

https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/28925

I have pushed a change that should get you booting to homescreen once it gets merged (or you can cherry-pick it).  Based on my investigation, I imagine things have been broken in a couple of ways for quite a while.  I have memories of at least boot testing the change to use linux-fslc-lts that I did back in Marlin with the switch to Yocto kirkstone, but I must have missed checking in the bbappend for linux-fslc-lts to pick up our AGL kernel configuration bits, and some things would have been a bit iffy without that.  My guess is that at some point after Marlin, linux-fslc-lts developed this boot issue, and we picked it up in one of our uprevs of meta-freescale.  I have compared the kernel configurations and devicetrees between linux-fslc and linux-fslc-lts, and nothing obvious jumps out there, so it's a bit of a puzzle why linux-fslc-lts does not work now.

All that, however, is a bit moot, as it turns out that the MHDP driver required to get HDMI output has still not been upstreamed to Linux mainline, so both linux-fslc and linux-fslc-lts can only drive the DSI outputs AFAICT.  So to get us back to a reasonable working state, I have restored a reworked version of what I was doing with YP dunfell pre-Marlin, i.e. using the hybrid linux-fslc-imx kernel with some tweaks to use etnaviv.  I have also restored an updated version of the imx8mq-evk-viv machine template that uses the NXP BSP option in meta-freescale and thus picks up the Vivante driver.  That can be used as a fallback for testing or if someone has access to NXP support.

One other thing to note is that Bluetooth seems broken, so I have disabled starting it up and opened https://lf-automotivelinux.atlassian.net/browse/SPEC-4807#icft=SPEC-4807 to track that.  It is unlikely that I look at that issue for a while due to needing to get other things done for the Pike release.

@Scott Murray  Is there a branch you are working on so we could pulll the changes you are making. 

I have managed to get my board to boot, but graphics are not working so more digging is required.  It looks like I missed checking in a bbappend last year when I switched the i.MX boards off of the default linux-fslc to linux-fslc-lts for AGL, but just adding it doesn't help with respect to this boot problem; it looks like linux-fslc-lts has either a kernel configuration or devicetree issue on the EVK.  Switching back to the upstream meta-freescale default of linux-fslc does get the board to boot, but no graphics as mentioned above.  I will investigate further tomorrow.