drm/amd/amdgpu: Add Descriptions to Process Isolation and Cleaner Shader Sysfs Functions

This update adds explanations to key functions related to process
isolation and cleaner shader execution sysfs interfaces.

- `amdgpu_gfx_set_run_cleaner_shader`: Describes how to manually run a
  cleaner shader, which clears the Local Data Store (LDS) and General
  Purpose Registers (GPRs) to ensure data isolation between GPU workloads.

- `amdgpu_gfx_get_enforce_isolation`: Describes how to query the current
  settings of the 'enforce_isolation' feature for each GPU partition.

- `amdgpu_gfx_set_enforce_isolation`: Describes how to enable or disable
  process isolation for GPU partitions through the sysfs interface.

Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Suggested-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>