Deprecation of AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED

[Marek Olšák]

Hi,

Given how our memory manager works and the guesswork that UMDs have to
do to determine whether to set the flag, I think the flag isn't
useful.

I'm proposing that CPU_ACCESS_REQUIRED:
- will be deprecated.
- It will remain to be accepted by the kernel driver, but it will
either not have any effect, or it will serve as a hint that might or
might not be followed.
- The only flag that UMDs are expected to set with regard to CPU
access is NO_CPU_ACCESS.

The main motivation is the reduction of "virtual" heaps for UMD buffer
suballocators and reusable buffer pools. A higher number of heaps
means that more memory can be wasted by UMDs.

Opinions?

Thanks,
Marek