agx: Plug memory leak in register allocator

Fixes: 85e18deb18 ("agx: Assign registers locally")
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reported-by: Coverity
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12053>

src/asahi/compiler/agx_register_allocate.c

@@ -236,6 +236,7 @@ agx_ra(agx_context *ctx)
       }
    }
 
+   free(ssa_to_reg);
    free(ncomps);
    free(alloc);
 }