rs6000: Correct documentation for __builtin_mtfsf

[Bill Schmidt]

Hi,

PR93570 reports that the documentation shows __builtin_mtfsf to return a double,
but that is incorrect.  The return signature should be void.  Corrected herein.

Built on powerpc64le-unknown-linux-gnu and verified correct PDF output.  
Committed
as obvious.

Thanks!
Bill


2020-02-06  Bill Schmidt  <wschm...@linux.ibm.com>

        PR target/93570
        * doc/extend.texi (Basic PowerPC Built-in Functions): Correct
        prototype for __builtin_mtfsf.

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index ec99c38a607..5739063b330 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -17166,7 +17166,7 @@ unsigned long __builtin_ppc_mftb ();
 double __builtin_unpack_ibm128 (__ibm128, int);
 __ibm128 __builtin_pack_ibm128 (double, double);
 double __builtin_mffs (void);
-double __builtin_mtfsf (const int, double);
+void __builtin_mtfsf (const int, double);
 void __builtin_mtfsb0 (const int);
 void __builtin_mtfsb1 (const int);
 void __builtin_set_fpscr_rn (int);