Follow parameter naming convention

Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
diff --git a/library/bignum_core.c b/library/bignum_core.c
index 473ef1a..233b22d 100644
--- a/library/bignum_core.c
+++ b/library/bignum_core.c
@@ -170,8 +170,8 @@
     mbedtls_ct_mpi_uint_cond_assign( limbs, X, A, assign );
 }
 
-void mbedtls_mpi_core_cond_swap( mbedtls_mpi_uint *A,
-                                 mbedtls_mpi_uint *B,
+void mbedtls_mpi_core_cond_swap( mbedtls_mpi_uint *X,
+                                 mbedtls_mpi_uint *Y,
                                  size_t limbs,
                                  unsigned char swap )
 {
@@ -180,9 +180,9 @@
 
     for( size_t i = 0; i < limbs; i++ )
     {
-        mbedtls_mpi_uint tmp = A[i];
-        A[i] = ( A[i] & ~limb_mask ) | ( B[i] & limb_mask );
-        B[i] = ( B[i] & ~limb_mask ) | (  tmp & limb_mask );
+        mbedtls_mpi_uint tmp = X[i];
+        X[i] = ( X[i] & ~limb_mask ) | ( Y[i] & limb_mask );
+        Y[i] = ( Y[i] & ~limb_mask ) | (  tmp & limb_mask );
     }
 }