drm: move to kref per-master structures.

This is step one towards having multiple masters sharing a drm
device in order to get fast-user-switching to work.

It splits out the information associated with the drm master
into a separate kref counted structure, and allocates this when
a master opens the device node. It also allows the current master
to abdicate (say while VT switched), and a new master to take over
the hardware.

It moves the Intel and radeon drivers to using the sarea from
within the new master structures.
Signed-off-by: Dave Airlie <airlied@redhat.com>

include/drm/drm_sarea.h

@@ -36,12 +36,12 @@
 
 /* SAREA area needs to be at least a page */
 #if defined(__alpha__)
-#define SAREA_MAX                       0x2000
+#define SAREA_MAX                       0x2000U
 #elif defined(__ia64__)
-#define SAREA_MAX                       0x10000	/* 64kB */
+#define SAREA_MAX                       0x10000U	/* 64kB */
 #else
 /* Intel 830M driver needs at least 8k SAREA */
-#define SAREA_MAX                       0x2000
+#define SAREA_MAX                       0x2000U
 #endif
 
 /** Maximum number of drawables in the SAREA */