dropbear: drop run time detection of read-only rootfs
Previously, when dropbear was started via its init script, relocation
of DROPBEAR_RSAKEY_DIR to support read-only rootfs was handled at
run time from within the init script.
Update the init script to take advantage of the read-only rootfs
config setup by read_only_rootfs_hook() and therefore be consistent
with startup under systemd (where relocation of DROPBEAR_RSAKEY_DIR
is handled by the read_only_rootfs_hook() at build time).
Signed-off-by: Andre McCurdy <armccurdy@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
