drm/amd/ras: Update ras command context structure name

drm/amd/ras: Update ras command context structure name

According to the actual usage of this structure,
it is more appropriate to call it context, the
structure name with ioctl is easy to cause
misunderstanding.

V2:
  Update commit message content.

Signed-off-by: YiPeng Chai <YiPeng.Chai@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>