Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC changes to atomic.h usage in DRM code

This commit follows the merge of atomic.h changes in r262807 and r262823.
The original work is from Jung-uk Kim (jkim@).

The following revisions were merged in this single commit:

r255009:
Fix a compiler warning. With this fix, a negative time can be converted to
a struct timeval and back to the original nanoseconds correctly.

r255012:
Fix a compiler warning and add couple of VM map types.

r255013:
Correct atomic operations in i915.

r255037:
Fix atomic operations on context_flag without altering semantics.

r255039:
- Remove test_and_set_bit() macro. It is unused since r255037.
- Relax atomic_read() and atomic_set() macros. Linux does not require any
memory barrier. Also, these macros may be even reordered or optimized away
according to the API documentation:

https://www.kernel.org/doc/Documentation/atomic_ops.txt

r255041:
Clarify confusions between atomic_t and bitmap. Fix bitmap operations
accordingly.

r255042:
Fix the incomplete conversion from atomic_t to long for test_bit().

r255044:
Partially revert r254880. The bitmap operations actually use long type now.

r255045:
'u_long' is consistently spelled 'unsigned long' in this file. Fix it.

MFC r235783:
Add the code for new Intel GPU driver, which supports GEM, KMS and
works with new generations of GPUs (IronLake, SandyBridge and
supposedly IvyBridge).

The driver is not connected to the build yet.

Add the code for new Intel GPU driver, which supports GEM, KMS and
works with new generations of GPUs (IronLake, SandyBridge and
supposedly IvyBridge).

The driver is not connected to the build yet.

Sponsored by: The FreeBSD Foundation
MFC after: 1 week