Replace -mfunction-return== with -mfunction-return=

Fix a typo in doc/invoke.texi.

	* doc/invoke.texi: Replace -mfunction-return==@var{choice} with
	-mfunction-return=@var{choice}.

From-SVN: r257124

gcc/ChangeLog

+2018-01-27  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* doc/invoke.texi: Replace -mfunction-return==@var{choice} with
+	-mfunction-return=@var{choice}.
+
 2018-01-27  Bernd Edlinger  <bernd.edlinger@hotmail.de>
 
 	PR diagnostic/84034

gcc/doc/invoke.texi

@@ -1232,7 +1232,7 @@ See RS/6000 and PowerPC Options.
 -mstack-protector-guard-offset=@var{offset} @gol
 -mstack-protector-guard-symbol=@var{symbol} -mmitigate-rop @gol
 -mgeneral-regs-only -mcall-ms2sysv-xlogues @gol
--mindirect-branch=@var{choice} -mfunction-return==@var{choice} @gol
+-mindirect-branch=@var{choice} -mfunction-return=@var{choice} @gol
 -mindirect-branch-register}
 
 @emph{x86 Windows Options}