amdkfd: Add mqd_manager module

The mqd_manager module handles MQD data structures.
MQD stands for Memory Queue Descriptor, which is used by the H/W to
keep the usermode queue state in memory.

v3:

Removed new typedefs
Removed pragma pack 4
Remove cik_mqds.h file
Changed lower_32/upper_32 calls to use linux macros
Used new gart allocation functions
Added documentation

v4:

Added missing initialization of the addr field in init_mqd()

Setting the hqd persistent.preload_req bit ON so that when queues switches
on/off, their context will kept and read from the mqd when the cp reassign
them, and thus the dispatched workload context kept consistent without any
interrupts.

v5:

Move amdkfd from drm/radeon/ to drm/amd/
Change format of mqd structure to match latest KV firmware
Add support for AQL queues creation to enable working with open-source HSA
runtime.
Various fixes

Signed-off-by: Ben Goz <ben.goz@amd.com>
Signed-off-by: Oded Gabbay <oded.gabbay@amd.com>