sparc: Move __fenv_{ld,st}fsr to fenv-private.h

These should not be exported on installed headers.

Checked on sparc64-linux-gnu and sparcv9-linux-gnu.

sysdeps/sparc/fpu/fegetround.c

@@ -17,6 +17,7 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <fenv.h>
+#include <fenv_private.h>
 
 int
 __fegetround (void)