mount.cifs: get rid of CONST_DISCARD

mount.cifs: get rid of CONST_DISCARD

Apparently, we need to strip the "const" attribute off of the mnt_fstype
before passing it to addmntent to prevent a (somewhat bogus) compiler
warning.

Rather than just stripping off the "const" attribute, clarify the code
by declaring a new non-const char pointer that points to the same
string. We can also use that same pointer in the mount(2) call too.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Matthias Dieter Wallnöfer <mdw@samba.org>