panfrost: do not artificially limit texture-sizes

We've been limiting the max texture size needlessly on Panfrost, which probably was a good idea back in the Midgard and GLES days. But these days, we can get systems with 32GB of memory and more, and limiting the texture size on these systems no longer makes as much sense.

Turns out, we already have a memory-saving mechanism in Mesa / Gallium, which can be controlled by the pipe_screen::can_create_resource-hook.

The decision to divide by the memory by four is copied from RadeonSI, but seems reasonable; if we assume 1GB of RAM, this limits us at 256MB, which is the same memory usage as a texture of 8192 x 8192 with 4 bytes per component. So not much changes in that case, and we mostly just allow larger textures on systems with more memory.

This allows us to support larger textures than 8192, which is especially useful to support OpenCL images with RustiCL.