MFC r293346:
Provide yet another KPI for cdev creation, make_dev_s(9).

MFC r280345:
Fix for out of order device destruction notifications when using the
delist_dev() function. In addition to this change:
- add a proper description of this function
- add a proper witness assert inside this function
- switch a nearby line to use the "cdp" pointer instead of cdev2priv()

MFC r277179, r277199 and r277391:
Add a kernel function to delist our kernel character devices, so that
the device name can be re-used right away in case we are destroying
the character devices in the background.

MFC r256885:
Remove global device lock acquisition from dev_relthread(), replacing it
with atomics on per-device data.

MFC r280345:
Fix for out of order device destruction notifications when using the
delist_dev() function. In addition to this change:
- add a proper description of this function
- add a proper witness assert inside this function
- switch a nearby line to use the "cdp" pointer instead of cdev2priv()

MFC r277179, r277199 and r277391:
Add a kernel function to delist our kernel character devices, so that
the device name can be re-used right away in case we are destroying
the character devices in the background.

MFC r256885:
Remove global device lock acquisition from dev_relthread(), replacing it
with atomics on per-device data.