init-install-efi.sh: Avoid /mnt/mtab creation if already present
The base-files recipe installs /mnt/mtab (it is a softlink of /proc/mounts),
so if an image includes the latter, there is no new to created it again inside
the install-efi.sh script, otherwise an error may occur as indicated on the
bug's site.
[YOCTO #7971]
(From OE-Core master rev:
6c6c6528954952e1e323f5a26afd93b99913e6f2)
Signed-off-by: Leonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Joshua Lock <joshua.lock@collabora.co.uk>
