drm/i915: fix i386 build of 64b raw_uncore functions

When building with ARCH=i386, readq and writeq are not defined,
resulting in:

intel_uncore.h: In function ‘__raw_uncore_read64’:
intel_uncore.h:257:9: error: implicit declaration of function ‘readq’;
	did you mean ‘readl’? [-Werror=implicit-function-declaration]
  return read##s__(uncore->regs + i915_mmio_reg_offset(reg)); \
         ^

and:

intel_uncore.h: In function ‘__raw_uncore_write64’:
intel_uncore.h:264:2: error: implicit declaration of function ‘writeq’;
	did you mean ‘writel’? [-Werror=implicit-function-declaration]
  write##s__(val, uncore->regs + i915_mmio_reg_offset(reg)); \
  ^

Add the io-64-nonatomic-lo-hi include to have readq and writeq available
for all builds. This header internally includes linux/io.h, so the
native readq and writeq definitions will be used when available.

Fixes: 6cc5ca76 ("drm/i915: rename raw reg access functions")
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190326233817.5417-1-daniele.ceraolospurio@intel.com

drivers/gpu/drm/i915/intel_uncore.h

@@ -28,6 +28,7 @@
 #include <linux/spinlock.h>
 #include <linux/notifier.h>
 #include <linux/hrtimer.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
 
 #include "i915_reg.h"