re PR target/51244 ([SH] Inefficient conditional branch and code around T bit)

re PR target/51244 ([SH] Inefficient conditional branch and code around T bit)

	PR target/51244
	* config/sh/sh.opt (mzdcbranch): New option.
	* doc/invoke.texi: Document it.
	* config/sh/sh.md (negsi_cond): Use TARGET_ZDCBRANCH as condition
	instead of TARGET_HARD_SH4.
	* config/sh/sh.c (sh_option_override): Set TARGET_ZDCBRANCH as default
	for TARGET_HARD_SH4.

From-SVN: r189877