[riscv64] Fix popcount

Change-Id: I0b7b4daf5b88341ba56076137b8d34bdfcd45c1a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3773329
Reviewed-by: ji qiu <qiuji@iscas.ac.cn>
Commit-Queue: ji qiu <qiuji@iscas.ac.cn>
Cr-Commit-Position: refs/heads/main@{#81860}

test/cctest/test-assembler-riscv64.cc

@@ -2813,7 +2813,7 @@ UTEST_VFIRST_M_WITH_WIDTH(8)
         __ vcpop_m(a0, v2);                                           \
       };                                                              \
       auto res = GenAndRunTest<int64_t, int64_t>((int64_t)src, fn);   \
-      CHECK_EQ(std::__popcount(src[0]), res);                         \
+      CHECK_EQ(__builtin_popcountl(src[0]), res);                     \
     }                                                                 \
   }