[RA]: Add flag for checking IRA in progress

[RA]: Add flag for checking IRA in progress

RISCV target developers need a flag to prevent creating
insns in IRA which can not be split after RA as they will need a
temporary reg.  The patch introduces such flag.

gcc/ChangeLog:

	* rtl.h (lra_in_progress): Change type to bool.
	(ira_in_progress): Add new extern.
	* ira.cc (ira_in_progress): New global.
	(pass_ira::execute): Set up ira_in_progress.
	* lra.cc: (lra_in_progress): Change type to bool and initialize.
	(lra): Use bool values for lra_in_progress.
	* lra-eliminations.cc (init_elim_table): Ditto.