Merge tag 'arc-for-2018.05-rc3' of git://git.denx.de/u-boot-arc

Subtle ARC fixes for v2018.05-RC3

These are only very subtle clean-ups here and there including:

 * Correctly specified CPU freq for HSDK
   (production boards are all shipped with 500MHZ as opposed
    to early batch running at 1GHz)

 * Addition of SNPS internal group email to MAINTAINERS file
 * Switch to Hush shell on AXS10x boards