Revert "base-files: add fstab for systemd based systems"

Revert "base-files: add fstab for systemd based systems"

For hybrid systemd/sysvinit builds, only one fstab can be used.
The default fstab used by sysvinit should work fine with systemd.

Since virtually every machine will ship its own fstab in its bsp
layer, the bsp layer may decide how to override the fstab based
on distro features.

This reverts commit 77bbb839ba25b974a538b90d346b454ccd5deefd.

(From OE-Core rev: e9352e8a43639564af0a97f5e8a642e0989b0256)

Signed-off-by: Andreas Oberritter <obi@opendreambox.org>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>