Bignum: move internal constants to headers

Now that the check_names script allows it, we can do so.

Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 07bd038..d9a1509 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -10,17 +10,7 @@
 #if MBEDTLS_MPI_MAX_BITS > 792
 #define MPI_MAX_BITS_LARGER_THAN_792
 #endif
-
-#define ciL    (sizeof(mbedtls_mpi_uint))   /* chars in limb  */
-#define biL    (ciL << 3)                   /* bits  in limb  */
-
-/*
- * Convert between bits/chars and number of limbs
- * Divide first in order to avoid potential overflows
- */
-#define BITS_TO_LIMBS(i)  ( (i) / biL + ( (i) % biL != 0 ) )
-#define CHARS_TO_LIMBS(i) ( (i) / ciL + ( (i) % ciL != 0 ) )
-
+#
 /* Check the validity of the sign bit in an MPI object. Reject representations
  * that are not supported by the rest of the library and indicate a bug when
  * constructing the value. */