VFS: prevent unmapping drivers that don't support reopening
VFS: prevent unmapping drivers that don't support reopening

libchardriver does not support DEV_REOPEN and will return ERESTART
when you do try it. This made VFS unhappy and concluded erroneously
that the driver was EDEADEPT.

veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi