Enable uint128 on riscv64

Fixes
| verified/kremlin/kremlib/dist/minimal/LowStar_Endianness.h:29:37: error: 'load128_be' declared 'static' but never defined [-Werror=unused-function]
|    29 | inline static FStar_UInt128_uint128 load128_be(uint8_t *x0);
|       |                                     ^~~~~~~~~~

Upstream-Status: Pending
Signed-off-by: Khem Raj <raj.khem@gmail.com>
--- a/nss/lib/freebl/verified/kremlin/include/kremlin/internal/types.h
+++ b/nss/lib/freebl/verified/kremlin/include/kremlin/internal/types.h
@@ -56,7 +56,8 @@ typedef const char *Prims_string;
 #include <emmintrin.h>
 typedef __m128i FStar_UInt128_uint128;
 #elif !defined(KRML_VERIFIED_UINT128) && !defined(_MSC_VER) && \
-    (defined(__x86_64__) || defined(__x86_64) || defined(__aarch64__))
+    (defined(__x86_64__) || defined(__x86_64) || defined(__aarch64__) || \
+     (defined(__riscv) && __riscv_xlen == 64))
 typedef unsigned __int128 FStar_UInt128_uint128;
 #else
 typedef struct FStar_UInt128_uint128_s {
--- a/nss/lib/freebl/verified/kremlin/kremlib/dist/minimal/fstar_uint128_gcc64.h
+++ b/nss/lib/freebl/verified/kremlin/kremlib/dist/minimal/fstar_uint128_gcc64.h
@@ -23,9 +23,10 @@
 #include "FStar_UInt128.h"
 #include "FStar_UInt_8_16_32_64.h"
 #include "LowStar_Endianness.h"
-
+#include <stdint.h>
 #if !defined(KRML_VERIFIED_UINT128) && !defined(_MSC_VER) && \
-    (defined(__x86_64__) || defined(__x86_64) || defined(__aarch64__))
+    (defined(__x86_64__) || defined(__x86_64) || defined(__aarch64__) || \
+     (defined(__riscv) && __riscv_xlen == 64))
 
 /* GCC + using native unsigned __int128 support */