drm/i915/guc: Drop guc2host/host2guc from names

drm/i915/guc: Drop guc2host/host2guc from names

To facilitate code reorganization we are renaming everything that
contains guc2host or host2guc.

host2guc_action() and host2guc_action_response() become guc_send()
and guc_recv() respectively.

Other host2guc_*() functions become simply guc_*().

Other entities are renamed basing on context they appear in:
 - HOST2GUC_ACTIONS_&           become INTEL_GUC_ACTION_*
 - HOST2GUC_{INTERRUPT,TRIGGER} become GUC_SEND_{INTERRUPT,TRIGGER}
 - GUC2HOST_STATUS_*            become INTEL_GUC_STATUS_*
 - GUC2HOST_MSG_*               become INTEL_GUC_RECV_MSG_*
 - action_lock                 becomes send_mutex

v2: drop unnecessary backslashes and use BIT() instead of '<<'
v3: shortened enum names and INTEL_GUC_STATUS_*

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480096777-12573-3-git-send-email-arkadiusz.hiler@intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>