target/loongarch: Fix helper_lddir() a CID INTEGER_OVERFLOW issue

When the lddir level is 4 and the base is a HugePage, we may try to put value 4
into a field in the TLBENTRY that is only 2 bits wide.

Fixes: Coverity CID 1547717
Fixes: 9c70db9a43 ("target/loongarch: Fix tlb huge page loading issue")
Signed-off-by: Song Gao <gaosong@loongson.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20240724015853.1317396-1-gaosong@loongson.cn>

target/loongarch/tcg/tlb_helper.c

@@ -525,6 +525,7 @@ target_ulong helper_lddir(CPULoongArchState *env, target_ulong base,
         if (unlikely(level == 4)) {
             qemu_log_mask(LOG_GUEST_ERROR,
                           "Attempted use of level 4 huge page\n");
+            return base;
         }
 
         if (FIELD_EX64(base, TLBENTRY, LEVEL)) {