drm-gem: Fix build

On some distros missing prototypes cause kernel builds to fail.  These
are hack to make the code build.

linux-core/i915_gem.c

@@ -30,6 +30,7 @@
 #include "drm_compat.h"
 #include "i915_drm.h"
 #include "i915_drv.h"
+#include <linux/swap.h>
 
 #define WATCH_COHERENCY	0
 #define WATCH_BUF	0

linux-core/i915_gem_tiling.c

@@ -30,6 +30,9 @@
 #include "i915_drm.h"
 #include "i915_drv.h"
 
+extern int pci_read_base(struct pci_dev *dev, unsigned int reg,
+    struct resource *res);
+
 /** @file i915_gem_tiling.c
  *
  * Support for managing tiling state of buffer objects.