ac: remove gallivm header include

this doesn't seem to be used

Acked-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16192>

src/amd/llvm/ac_llvm_util.c

@@ -27,7 +27,6 @@
 
 #include "ac_llvm_build.h"
 #include "c11/threads.h"
-#include "gallivm/lp_bld_misc.h"
 #include "util/bitscan.h"
 #include "util/u_math.h"
 #include <llvm-c/Core.h>