[PATCH v3] target/arm: Fix compile error in gcc 4.9.4.

[Kaige Li]

Error log:

/home/LiKaige/qemu/target/arm/translate-a64.c: In function ‘disas_ldst’:
/home/LiKaige/qemu/target/arm/translate-a64.c:3392:5: error: ‘fn’ may be used 
uninitialized in this function [-Werror=maybe-uninitialized]
     fn(cpu_reg(s, rt), clean_addr, tcg_rs, get_mem_index(s),
     ^
/home/LiKaige/qemu/target/arm/translate-a64.c:3318:22: note: ‘fn’ was declared 
here
     AtomicThreeOpFn *fn;
                      ^
cc1: all warnings being treated as errors

Add an initiallization value NULL for fn to fix this.

Signed-off-by: Kaige Li <likaige@loongson.cn>
---
 target/arm/translate-a64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
index 8c07649..c98dfb1 100644
--- a/target/arm/translate-a64.c
+++ b/target/arm/translate-a64.c
@@ -3315,7 +3315,7 @@ static void disas_ldst_atomic(DisasContext *s, uint32_t 
insn,
     bool r = extract32(insn, 22, 1);
     bool a = extract32(insn, 23, 1);
     TCGv_i64 tcg_rs, clean_addr;
-    AtomicThreeOpFn *fn;
+    AtomicThreeOpFn *fn = NULL;
 
     if (is_vector || !dc_isar_feature(aa64_atomics, s)) {
         unallocated_encoding(s);
-- 
2.1.0