Move RTEMS target configuration to ELF sections

bfd/
	* config.bfd (powerpcle-*-rtems*): Do not mark as removed.
	(arm-*-rtems*): Move to (arm*-*-eabi*).
	(i[3-7]86-*-rtems*): Move to (i[3-7]86-*-elf*).
	(m68-*-rtems*): Move to (m68*-*-elf*).
ld/
	* configure.tgt (arm-*-rtems*): Move to (arm*-*-eabi*).
	(bfin-*-rtems*): Move to (bfin*-*-elf*).
	(i[3-7]86-*-rtems*): Move to (i[3-7]86*-*-elf*).
	(m68*-*-rtems*): Move to (m68*-*-elf*).
	(mips*-*-rtems*): Move to (mips*-*-elf*).
	(or1k*-*-rtems*): Move to (or1k*-*-elf*).
	(powerpc*-*-rtems*): Move to (powerpc*-*-elf*).
	(sparc*-*-rtems*): Move to (sparc*-*-elf*).
	(sparc64*-*-rtems*): Move to (sparc64*-*-elf*).