pru: libm: Fix incorrect function name

Upstream GCC changed -Wimplicit-function-declaration warning into an
error. The build break about missing fpclassifyf function prototype
exposed a bug in the PRU port of libm.

The fix is to use the fpclassify macro for both double and float types.

Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>

newlib/libm/machine/pru/fpclassifyf.c

@@ -32,5 +32,5 @@
    by TI ABI.  */
 int __pruabi_fpclassifyf(float a)
 {
-  return fpclassifyf(a);
+  return fpclassify(a);
 }