v3dv: rename and make compute_tile_size_for_framebuffer() public

We will use this when we implement copying images to buffers using the
TLB, where we'll need to setup a framebuffer and tiling configuration
for the TLB store to the destination buffer.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6766>
2 files changed