powerpc: Remove buggy 9-year-old test for binutils < 2.12.1

Recent binutils refuses to assemble AltiVec opcodes when in e500/SPE
mode, as some of those opcodes alias the "SPE" instructions.  This
triggers an ancient binutils version check even when building a kernel
with CONFIG_ALTIVEC disabled.

In theory, the check could be conditionalized on CONFIG_ALTIVEC, but in
practice it has long outlived its utility.  It is virtually impossible
to find binutils older than 2.12.1 (released 2002) in the wild anymore.
Even ancient RedHat Enterprise Linux 4 has binutils-2.14.

To fix the kernel build when done natively on e500 systems with this new
binutils, the test is simply removed.

Signed-off-by: Kyle Moffett <Kyle.D.Moffett@boeing.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>