drm/i915: Don't use BIT() in UAPI section

Lets not introduce BIT() macro requirement for UAPI for now.

Fixes: 3fd3a6ff ("drm/i915: Simplify i915_reg_read_ioctl")
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171006104559.17312-1-joonas.lahtinen@linux.intel.com

include/uapi/drm/i915_drm.h

@@ -1318,7 +1318,7 @@ struct drm_i915_reg_read {
 	 * be specified
 	 */
 	__u64 offset;
-#define I915_REG_READ_8B_WA BIT(0)
+#define I915_REG_READ_8B_WA (1ul << 0)
 
 	__u64 val; /* Return value */
 };