vc4: Make sure to emit a tile coordinates between two MSAA loads.

vc4: Make sure to emit a tile coordinates between two MSAA loads.

The HW only executes a load once the tile coordinates packet happens, and
only tracks one at a time, so by emitting our two MSAA loads back to back
we would end up with an undefined color or Z buffer.  The simulator
doesn't seem to care, but sync up the RCL generation with the kernel
anyway.

Fixes dEQP-EGL.functional.render.multi_context.gles2.rgb888_window