Remove global call sets: caller-save.c

Remove global call sets: caller-save.c

All caller-save.c uses of "|= fixed_reg_set" added in a previous patch
were redundant, since the sets are later ANDed with ~fixed_reg_set.

2019-09-30  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* caller-save.c (setup_save_areas): Remove redundant |s of
	fixed_reg_set.
	(save_call_clobbered_regs): Likewise.  Use the call ABI rather
	than call_used_or_fixed_regs to decide whether a REG_RETURNED
	value is useful.

From-SVN: r276313