Replace remaining byte shift with macro

Replace another instance of >> 8 with MBEDTLS_BYTE_1

Signed-off-by: Joe Subbiani <joe.subbiani@arm.com>
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 02c55af..49b7bc0 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -1208,8 +1208,8 @@
         MBEDTLS_SSL_DEBUG_MSG( 3, ( "adding FALLBACK_SCSV" ) );
 
         MBEDTLS_SSL_CHK_BUF_PTR( p, end, 2 );
-        *p++ = (unsigned char)( MBEDTLS_SSL_FALLBACK_SCSV_VALUE >> 8 );
-        *p++ = (unsigned char)( MBEDTLS_SSL_FALLBACK_SCSV_VALUE      );
+        *p++ = MBEDTLS_BYTE_1( MBEDTLS_SSL_FALLBACK_SCSV_VALUE );
+        *p++ = MBEDTLS_BYTE_0( MBEDTLS_SSL_FALLBACK_SCSV_VALUE );
         n++;
     }
 #endif