Remove unused parameter

Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
diff --git a/library/bignum_core.h b/library/bignum_core.h
index a538ece..779fb08 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -123,9 +123,8 @@
  *                 values different to either of the original ones.
  */
 void mbedtls_mpi_core_cond_swap( mbedtls_mpi_uint *X,
-                                 size_t X_limbs,
                                  mbedtls_mpi_uint *Y,
-                                 size_t Y_limbs,
+                                 size_t limbs,
                                  unsigned char swap );
 
 /** Import X from unsigned binary data, little-endian.