drm/i915/guc: Turn on GuC/HuC auto mode

drm/i915/guc: Turn on GuC/HuC auto mode

Using "enable_guc" modparam auto mode (-1) will let driver
decide on which platforms and in which configuration we want
to use GuC/HuC firmwares.

Today driver will enable HuC firmware authentication by GuC
only on Gen11+ platforms as HuC firmware is required to unlock
advanced video codecs in media driver.

Legacy platforms with GuC/HuC are not affected by this change
as for them driver still defaults to disabled(0) in auto mode.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190712111445.21040-3-michal.wajdeczko@intel.com