drm/amdgpu: Fix amdgpu_ip_block_hw_fini()

This NULL check is reversed so the function doesn't work.

Fixes: dad01f93 ("drm/amdgpu: validate hw_fini before function call")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/f4fc849e-4e76-4448-8657-caa4c69910b0@stanley.mountain


Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>