linux-phytec-ti

mtdchar: kill persistently held vfsmount

... and mtdchar_notifier along with it; just have ->drop_inode() that
will unconditionally get evict them instead of dances on mtd device
removal and use simple_pin_fs() instead of kern_mount()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>