Test SEC_HAS_CONTENTS in relax routines

Test SEC_HAS_CONTENTS in relax routines

More places that generally expect instructions, so not zeros.

	* coff-sh.c (sh_relax_section, sh_relax_delete_bytes): Exclude
	sections without SEC_HAS_CONTENTS set.
	* elf-m10200.c (mn10200_elf_relax_section): Likewise.
	* elf32-arc.c (arc_elf_relax_section): Likewise.
	* elf32-avr.c (elf32_avr_relax_section): Likewise.
	* elf32-cr16.c (elf32_cr16_relax_section): Likewise.
	* elf32-crx.c (elf32_crx_relax_section): Likewise.
	* elf32-epiphany.c (epiphany_elf_relax_section): Likewise.
	* elf32-ft32.c (ft32_elf_relax_section): Likewise.
	* elf32-h8300.c (elf32_h8_relax_section): Likewise.
	* elf32-ip2k.c (ip2k_elf_relax_section): Likewise.
	* elf32-m32c.c (m32c_elf_relax_section): Likewise.
	* elf32-m68hc11.c (m68hc11_elf_relax_section): Likewise.
	* elf32-msp430.c (msp430_elf_relax_section): Likewise.
	* elf32-pru.c (pru_elf32_relax_section): Likewise.
	* elf32-rl78.c (rl78_elf_relax_section): Likewise.
	* elf32-rx.c (elf32_rx_relax_section): Likewise.
	* elf32-sh.c (sh_elf_relax_section): Likewise.
	(sh_elf_relax_delete_bytes): Likewise.
	* elf32-v850.c (v850_elf_relax_section): Likewise.
	* elf64-alpha.c (elf64_alpha_relax_section): Likewise.
	* elf64-ia64-vms.c (elf64_ia64_relax_section): Likewise.
	* elfnn-ia64.c (elfNN_ia64_relax_section): Likewise.
	* elfnn-riscv.c (_bfd_riscv_relax_section): Likewise.
	* elfxx-mips.c (_bfd_mips_elf_relax_section): Likewise.