ld/arc: Make little endian default choice for linker scripts

ld/arc: Make little endian default choice for linker scripts

When building with --enable-targets=all the target string is not set to
something that matches the pattern arc*-*, and so the script used to
decide if we should build big or little endian linker script currently
exits with an error.

This commit makes little endian linker script be the default, which will
be used when building for all targets, this matches the behaviour from
before I made the endianness switchable, when we only ever built little
endian linker scripts anyway.

ld/ChangeLog:

	* emulparams/arc-endianness.sh: Make little endian default choice.