drm/amdgpu: fix bo->pin leaking in amdgpu_bo_create_reserved

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu: fix bo->pin leaking in amdgpu_bo_create_reserved amdgpu_bo_create_reserved() only allocates a new BO when *bo_ptr (struct amdgpu_bo **bo_ptr as input parameter) is NULL, it simply skips creation when *bo_ptr is non-NULL. But it unconditionally reserves, pins, gart allocates and maps the BO afterwards. When the same non-NULL BO pointer is passed in again, for example firmware buffers that live in adev and are re-loaded on every resume / cp_resume / start under AMDGPU_FW_LOAD_DIRECT, amdgpu_bo_pin() just increases pin_count unconditionally, however the matching teardown only unpins once, so pin_count never drops to zero, so TTM is not able to move, swap or evict a BO, causing BO leaks. This commit fixes this issue by only pinning the bo once at creation, and repeated calls no longer take additional pin references. (cherry picked from commit 3ddc0ae76202c447b6aec61e907b852bc94671cf)