nv50: free interpolation parameters in nv50_program_destroy()

As for nvc0, we need to free memory allocated by interpolation
parameters. This fixes a memory leak spotted by valgrind.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>

src/gallium/drivers/nouveau/nv50/nv50_program.c

@@ -489,7 +489,7 @@ nv50_program_destroy(struct nv50_context *nv50, struct nv50_program *p)
    FREE(p->code);
 
    FREE(p->fixups);
-
+   FREE(p->interps);
    FREE(p->so);
 
    memset(p, 0, sizeof(*p));