Increase loop alignment on Cortex cores to 8 and set function alignment to 16.

Increase loop alignment on Cortex cores to 8 and set function alignment to 16.

This makes things consistent across big.LITTLE cores, improves performance of
benchmarks with tight loops and reduces performance variations due to small
changes in code layout.

    gcc/
        * config/aarch64/aarch64.c (cortexa53_tunings):
        Increase loop alignment to 8.  Set function alignment to 16.
        (cortexa35_tunings): Likewise.
        (cortexa57_tunings): Increase loop alignment to 8.
        (cortexa72_tunings): Likewise.
        (cortexa73_tunings): Likewise.

From-SVN: r237851