binutils: enable as target package for aarch64

binutils: enable as target package for aarch64

binutils got disabled as a target package for aarch64 back in Buildroot
2012.11 (commit 660d16f4).
The default version 2.21.1 at the time didn't really support aarch64, as
shown by the autobuilder error reference in that commit.

binutils has now had support for aarch64 since 2.23, but was never
re-enabled for aarch64.

All of the binutils versions currently supported by Buildroot (oldest
being 2.24) support aarch64, so we can now enable it without any
restrictions.

This same patch also touches the dropwatch, lightning and oprofile
packages which all select binutils and had the 'depends on !aarch64' to
keep Kconfig consistent. They are now re-enabled for aarch64 as well.
They are changed in this same patch so that Kconfig is kept consistent
and doesn't end up having them disabled in a commit which only has the
binutils change applied.
lightning has other explicit arch dependencies so it is not actually yet
available in aarch64, but at least the dependency on !aarch64 because of
binutils is not needed anymore.

Everything has been build tested with Buildroot and external toolchains.
binutils and dropwatch work fine in a qemu target. oprofile doesn't seem
to be supported in the qemu aarch64 processor but builds fine and seems
to have some level of aarch64 support in the source, so there doesn't
seem to be a reason to keep it disabled in Kconfig.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>