Rename duplicate_loop_to_header_edge to duplicate_loop_body_to_header_edge

Rename duplicate_loop_to_header_edge to duplicate_loop_body_to_header_edge

gcc/ChangeLog:

2021-11-01  Xionghu Luo  <luoxhu@linux.ibm.com>

	* cfghooks.c (cfg_hook_duplicate_loop_to_header_edge): Rename
	duplicate_loop_to_header_edge to
	duplicate_loop_body_to_header_edge.
	(cfg_hook_duplicate_loop_body_to_header_edge): Likewise.
	* cfghooks.h (struct cfg_hooks): Likewise.
	(cfg_hook_duplicate_loop_body_to_header_edge): Likewise.
	* cfgloopmanip.c (duplicate_loop_body_to_header_edge): Likewise.
	(clone_loop_to_header_edge): Likewise.
	* cfgloopmanip.h (duplicate_loop_body_to_header_edge): Likewise.
	* cfgrtl.c (struct cfg_hooks): Likewise.
	* doc/loop.texi: Likewise.
	* loop-unroll.c (unroll_loop_constant_iterations): Likewise.
	(unroll_loop_runtime_iterations): Likewise.
	(unroll_loop_stupid): Likewise.
	(apply_opt_in_copies): Likewise.
	* tree-cfg.c (struct cfg_hooks): Likewise.
	* tree-ssa-loop-ivcanon.c (try_unroll_loop_completely): Likewise.
	(try_peel_loop): Likewise.
	* tree-ssa-loop-manip.c (copy_phi_node_args): Likewise.
	(gimple_duplicate_loop_body_to_header_edge): Likewise.
	(tree_transform_and_unroll_loop): Likewise.
	* tree-ssa-loop-manip.h (gimple_duplicate_loop_body_to_header_edge):
	Likewise.