Use mipsel- rather than mips- in directories involving mipsel ports to

	Use mipsel- rather than mips- in directories involving mipsel ports to
	allow both endiannesses coexist.

	* configure.ac: proparate target_cpu=mipsel rather than resetting to
	mips. All conditions adjusted.
	* tests/util/grub-shell-tester.in: Remove gratuitious target_cpu
	variable.
	* util/grub-install.in: Adjust conditions to take renaming into account.
	* util/grub-mkimage.c (image_targets): Likewise. New target
	mips-qemu_mips-elf for bigendian mips.