[RS6000] Don't pass --oformat to ld

[RS6000] Don't pass --oformat to ld

ld -m options select a particular ld emulation (e*.c files in ld build
dir) which provides a compiled-in scripts or select a script from
ldscripts/.  Each of these has an OUTPUT_FORMAT statement, which does
the same thing as --oformat.  --oformat is therefore redundant when
using GNU ld built this century, except possibly when overriding the
default ld scripts with -T.

	* config/rs6000/sysv4le.h (LINK_TARGET_SPEC): Don't define.
	* config/rs6000/sysv4.h (LINK_TARGET_SPEC): Likewise.
	(LINK_SPEC, SUBTARGET_EXTRA_SPECS): Delete link_target.

From-SVN: r227397