pmb/config: check CROSS_MEMORY_ATTACH config required for Waydroid

Without this syscall zygote keeps constantly crashing in the container.

Checked locally that all relevant kernels pass with this new requirement with:

for k in $(grep -r $(pmbootstrap config aports) -e pmb:kconfigcheck-anbox | cut -d':' -f1 | rev | cut -d'/' -f2 | rev | xargs); do
	pmbootstrap kconfig check --anbox $k
done