Revert "drm/i915/execlists: Reset RING registers upon resume"

This reverts commit f2a0409a which is
commit bafb2f7d4755bf1571bd5e9a03b97f3fc4fe69ae upstream.

It was reported to have problems.

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Eric Blau <eblau1@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>