libev: add patch to fix build on SPARCv8

Due to a mistake in a compile time conditional, SPARCv9 code was being
compiled in libev on a SPARCv8 system. A newly added patch fixes this,
which fixes the following build failure:

  http://autobuild.buildroot.net/results/55d6190b60a08c9bc4d659cf009df52388db676a/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>