gstreamer1: fix unaligned detection for nios2

Fixes:
http://autobuild.buildroot.net/results/cc6/cc6a6cab4f8c405941a71c6665a7dc2e34c39cb9/
http://autobuild.buildroot.net/results/2a3/2a350ac8be87a25d7f87f240943c816932f80a14/



Similar to how we do it for arc/xtensa/microblaze.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>