ARC: Add automake to the list of dependencies

Ubuntu package 'automake' is required to build OpenOCD (specifically to make 'bootstrap') but it was missing from ARC readme file. I guess that at some point automake was a dependency for a libtool, autoconfigure or build-essential, but as of Ubuntu 13.04 that is not the case, so I've added an explicit mention of this package to readme.
ARC: Update documentation according to user feedback.

* Add "cd" commands where required
* Remove unnecessary invocations of Digilent utilities which might confuse user
* Do not "make clean" before bootstrap
* Maintainer mode is required when building from Git tree
Merge remote branch 'origin/arc-0.7.0-dev-00222' into arc-0.7.0-dev-00222
Merge branch 'arc-0.7.0-dev-00222' of github.com:foss-for-synopsys-dwc-arc-processors/openocd into arc-0.7.0-dev-00222
Merge branch 'arc-0.7.0-dev-00222' of github.com:foss-for-synopsys-dwc-arc-processors/openocd into arc-0.7.0-dev-00222