gcc: invoke: delete -mno-fma4 docs

We don't document the -mno-xxx variants for other flags here, and the
paragraph here specifically says "Each has a corresponding -mno- option
to disable use of these instructions".  Drop the -mno-fma4 line.

From-SVN: r233144

gcc/ChangeLog

+2016-02-04  Mike Frysinger  <vapier@gentoo.org>
+
+	* doc/invoke.texi: Delete -mno-fma4.
+
 2016-02-04  Richard Sandiford  <richard.sandiford@arm.com>
 
 	PR rtl-optimization/69577

gcc/doc/invoke.texi

@@ -23462,9 +23462,6 @@ preferred alignment to @option{-mpreferred-stack-boundary=2}.
 @itemx -mfma4
 @opindex mfma4
 @need 200
-@itemx -mno-fma4
-@opindex mno-fma4
-@need 200
 @itemx -mprefetchwt1
 @opindex mprefetchwt1
 @need 200