drm/i915: Disable preemption and sleeping while using the punit sideband

While we talk to the punit over its sideband, we need to prevent the cpu
from sleeping in order to prevent a potential machine hang.

Note that by itself, it appears that pm_qos_update_request (via
intel_idle) doesn't provide a sufficient barrier to ensure that all core
are indeed awake (out of Cstate) and that the package is awake. To do so,
we need to supplement the pm_qos with a manual ping on_each_cpu.

v2: Restrict the heavy-weight wakeup to just the ISOF_PORT_PUNIT, there
is insufficient evidence to implicate a wider problem atm. Similarly,
restrict the w/a to Valleyview, as Cherryview doesn't have an angry cadre
of users.

The working theory, courtesy of Ville and Hans, is the issue lies within
the power delivery and so is likely to be unit and board specific and
occurs when both the unit/fw require extra power at the same time as the
cpu package is changing its own power state.

References: https://bugzilla.kernel.org/show_bug.cgi?id=109051
References: https://bugs.freedesktop.org/show_bug.cgi?id=102657
References: https://bugzilla.kernel.org/show_bug.cgi?id=195255


Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190426081725.31217-1-chris@chris-wilson.co.uk