cam_periph: Return ENXIO when peripheral is invalidated

When the peripheral is invalidated, no further I/O is possible. Signal
this up the stack with ENXIO now that upper layers of the stack
differentiate sometimes. In order for there to be further I/O, and new
open is required for any block device that a future periph might
instantiate for devices at this location that might return or otherwise
become available. The I/O scheduler flushes its I/O with the ENXIO error
for pending I/O that didn't make it to the device, so this makes the two
paths match.

MFC After: 3 days
Sponsored by: Netflix
Reviewed by: chs, mav
Differential Revision: https://reviews.freebsd.org/D35093

(cherry picked from commit 9fb40baf60435c000415429220c57c754ce318fd)