Prepare for Anbox: require ashmem, binder, squashfs in all kernels

@PureTryOut wrote in !432 (comment 197045302)

Can we maybe start making the ashmem and binder kernel options required before Anbox support is fully finished? It'll make live easier for developing this when there are kernel updates and stuff.

Yes, let's do this!

The proper way to do it is:

1. change the necessary kconfig options
2. run pmbootstrap kconfig check to see which kernels are not passing this check
3. fix up the kernel configs of all failing kernels (then check again, until it stops complaining)
4. increase the pkgrel of all kernels that were changed (e.g. with pmbootstrap pkgrel_bump $(git diff --name-only | cut -d/ -f 2) from pmaports.git root dir)
5. build all kernels that were changed (e.g. pmbootstrap build --strict --force $(git diff --name-only | cut -d/ -f 2))
6. create a merge request to pmaports.git with the changed kernels
7. create a MR to pmbootstrap.git with the new required kconfig options (change from 1.)

@PureTryOut: can you list which kernel options are exactly necessary for ashmem, binder and squashfs?