Remove redundant fixed_regs tests

Remove redundant fixed_regs tests

This patch removes redundant fixed_regs tests in things like:

  !fixed_regs[i] && !call_used_or_fixed_reg_p (i)

2019-09-10  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/alpha/alpha.c (alpha_compute_frame_layout): Remove redundant
	fixed_regs test.
	* config/bpf/bpf.c (bpf_compute_frame_layout, bpf_expand_prologue)
	(bpf_expand_epilogue): Likewise.
	* config/c6x/c6x.c (c6x_save_reg): Likewise.
	* config/ft32/ft32.c (ft32_expand_prologue): Likewise.
	(ft32_expand_epilogue): Likewise.
	* config/i386/i386.c (ix86_save_reg): Likewise.
	* config/moxie/moxie.c (moxie_expand_prologue): Likewise.
	(moxie_expand_epilogue): Likewise.
	* config/tilegx/tilegx.c (need_to_save_reg): Likewise.
	* config/tilepro/tilepro.c (need_to_save_reg): Likewise.
	* config/xtensa/xtensa.c (xtensa_call_save_reg): Likewise.

From-SVN: r275603