evas: move EVAS_CPU_TWEAKS to target EXTRA_OECONF

* it was causing different sstate checksum for evas-native
  $ bitbake-diffsigs
    stamps.1347348593/nokia900/x86_64-linux/evas-native-2_1.7.0-r0.0.do_configure.sigdata.cc8b80e938b87ad1bb8d6ded52ef941f
    stamps.1347348593/om-gta02/x86_64-linux/evas-native-2_1.7.0-r0.0.do_configure.sigdata.e6143417eb7ea0ebd0ab299ce5a024ea
      basehash changed from f453b3bdd276ffd49445d1c81e2962e8 to 3a244a9f14657439d5b4a8c7d609b087
      Variable EVAS_CPU_TWEAKS value changed from --disable-cpu-neon to

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>