mpi_core_mod_exp: improve style and documentation

No intended change in behaviour.

Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/library/bignum_core.h b/library/bignum_core.h
index ede8161..58a9f5a 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -503,21 +503,21 @@
  *                 X = A^E mod N
  *
  * \param[out] X   The destination MPI, as a little endian array of length
- *                 \p limbs.
- * \param[in] A    The base MPI, as a little endian array of length \p limbs.
- * \param[in] N    The modulus, as a little endian array of length \p limbs.
- * \param limbs    The number of limbs in \p X, \p A, \p N, \p RR.
+ *                 \p AN_limbs.
+ * \param[in] A    The base MPI, as a little endian array of length \p AN_limbs.
+ * \param[in] N    The modulus, as a little endian array of length \p AN_limbs.
+ * \param AN_limbs The number of limbs in \p X, \p A, \p N, \p RR.
  * \param[in] E    The exponent, as a little endian array of length \p E_limbs.
  * \param E_limbs  The number of limbs in \p E.
  * \param[in] RR   The precomputed residue of 2^{2*biL} modulo N, as a little
- *                 endian array of length \p limbs.
+ *                 endian array of length \p AN_limbs.
  *
  * \return         \c 0 if successful.
  * \return         #MBEDTLS_ERR_MPI_ALLOC_FAILED if a memory allocation failed.
  */
 int mbedtls_mpi_core_exp_mod( mbedtls_mpi_uint *X,
                               const mbedtls_mpi_uint *A,
-                              const mbedtls_mpi_uint *N, size_t limbs,
+                              const mbedtls_mpi_uint *N, size_t AN_limbs,
                               const mbedtls_mpi_uint *E, size_t E_limbs,
                               const mbedtls_mpi_uint *RR );