Revert "Add missing modem links"

This reverts commit 2f5a97f2e9cfb3e63fab74d43907e8e0c88a8773.
Revert "mount system read-only"

This reverts commit c8fff1257ff05e8fd4296d0d75367bcd3b15bba3.
Revert "m7-common: Remove modem links, generate firmware symlinks"

This reverts commit 6fc254e30732143e9c641c23b89526273e3397e8.