[fsbl] add fsbl for cv181x/cv180x

Change-Id: I6809bc5016d4bc148f62be2ed3f8e928ec111f19

fsbl/lib/libtommath/bn_mp_get_double.c

@@ -0,0 +1,31 @@
+#include "tommath_private.h"
+#ifdef BN_MP_GET_DOUBLE_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis
+ *
+ * LibTomMath is a library that provides multiple-precision
+ * integer arithmetic as well as number theoretic functionality.
+ *
+ * The library was designed directly after the MPI library by
+ * Michael Fromberger but has been written from scratch with
+ * additional optimizations in place.
+ *
+ * SPDX-License-Identifier: Unlicense
+ */
+
+double mp_get_double(const mp_int *a)
+{
+   int i;
+   double d = 0.0, fac = 1.0;
+   for (i = 0; i < DIGIT_BIT; ++i) {
+      fac *= 2.0;
+   }
+   for (i = USED(a); i --> 0;) {
+      d = (d * fac) + (double)DIGIT(a, i);
+   }
+   return (mp_isneg(a) != MP_NO) ? -d : d;
+}
+#endif
+
+/* ref:         $Format:%D$ */
+/* git commit:  $Format:%H$ */
+/* commit time: $Format:%ai$ */