drm/amdgpu: Move amdgpu_vm_is_bo_always_valid() before first use

drm/amdgpu: Move amdgpu_vm_is_bo_always_valid() before first use

Smatch reports that 'bo' could be NULL in amdgpu_vm_bo_update(), even
though amdgpu_vm_is_bo_always_valid() already checks for a NULL BO.

Move amdgpu_vm_is_bo_always_valid() earlier in the file so the helper
definition appears before its first use. This allows static analysis
tools to see the NULL check performed by the helper and avoids the
warning.

Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>