broadcom/compiler: define max number of tmu spills for compile strategies

Instead of whether they are allowed to spill or not. This is more flexible.
Also, while we are not currently enabling spilling on any 4-thread strategies,
should we do that in the future, always prefer a 4-thread compile.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15041>

src/broadcom/compiler/v3d_compiler.h

@@ -710,7 +710,7 @@ struct v3d_compile {
          * strategies that can reduce register pressure and hopefully reduce or
          * eliminate TMU spills in the shader.
          */
-        bool tmu_spilling_allowed;
+        uint32_t max_tmu_spills;
 
         /* The UBO index and block used with the last unifa load, as well as the
          * current unifa offset *after* emitting that load. This is used to skip