drm sync objects (vn+1)

[Dave Airlie]

Okay another day, another sync object patchset.

In my drm-syncobj branch.

This round should:
a) address the amdgpu CS ERESTARTSYS failure case, I've reworked
the sync_file/syncobj/amdgpu bits to have a lookup and just replace
in separate phases and just do the wait lookup and sync, then later
replace the waits with NULL, once the CS is submitted.

b) Block polling on the semaphore sync files, and cease worrying
about the polling state and callback when doing the replace fence
dance, which can only be called on semaphore sync files.

c) Add IGT tests - in my fd.o intel-gpu-tools repo syncobj branch,
are a basic sets of tests to do bad things and poke some corner
cases, and I've fixed up most of these in here hopefully. Checks
that padding is 0, legal fds, poll doesn't work etc.

d) bump SYNCOBJ CAP to 0x13 as 0x12 is already in use in drm-next.

Dave.