asahi,agx: Upload constant buffers immediately
The lifetime of the constant buffer's user_buffer is not guaranteed
to last until agx_upload_uniforms.
Fixes the same ASAN issue mesa/mesa!21685 is trying to address.
@alyssa might address this issue in mesa common code. That would supersede this merge request and potentially fixes the same issue in other drivers.
Fixes: 080b05e2 ("asahi: Add Gallium driver")
Signed-off-by: Janne Grunau j@jannau.net