lib/intel_mmio: Fix the fix

lib/intel_mmio: Fix the fix

commit 16e44f5499e1754dfb10fc62b22675f5aa6ac781
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Wed Apr 3 00:22:41 2013 +0200

    lib: fixup register access on gen2/3

THis fix was incorrect for a few reasons:
1. It didn't reflect the state in mmio_data.safe
2. It skipped forcewake on gen6+ which is both incorrect and
unnecessary (for gen<6).
3. It had 2 goto done, the second of which was impossible to hit.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>