radv: Fix output for sparse MRTs.

We need to init the cb_shader_format correctly with the changed
col_format, so this moves the col_format adjustment to before the
adjustment to before the cb_shader_mask gets generated.

Fixes: 06d3c650 "radv: fix a GPU hang when MRTs are sparse"
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106903


CC: 18.1 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
(cherry picked from commit 41dabdc4)