igt/gem_workarounds: igt to test workaround registers

igt/gem_workarounds: igt to test workaround registers

Some of the workarounds are lost followed by a gpu reset, suspend/resume;
this patch adds a test which compares register state before and after
the test scenario.

This test currently verifies only bdw workarounds.

v2: address patch cleanup comments (ThomasW)
 Add binary to ignore list and use igt_debugfs helper fns
 to read debugfs file and igt_info for printing debug info.

v2.1: address minor comments from Daniel
 use igt_main as opposed to normal main

Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com>
[danvet: Drop igt_exit, it's already in igt_main.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>