drm/i915/audio: add register macros for audio config N value

Have generic macros in line with the rest of the register bit definition
macros instead of a dedicated function in intel_audio.c, and use them.
No functional changes.

Cc: Libin Yang <libin.yang@linux.intel.com>
Reviewed-by: Libin Yang <libin.yang@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/c8709b065ba5cb91b85c54f4e099219e4e68b192.1476111629.git.jani.nikula@intel.com
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index acc767a..595d196 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -7332,6 +7332,10 @@
 #define   AUD_CONFIG_UPPER_N_MASK		(0xff << 20)
 #define   AUD_CONFIG_LOWER_N_SHIFT		4
 #define   AUD_CONFIG_LOWER_N_MASK		(0xfff << 4)
+#define   AUD_CONFIG_N_MASK			(AUD_CONFIG_UPPER_N_MASK | AUD_CONFIG_LOWER_N_MASK)
+#define   AUD_CONFIG_N(n) \
+	(((((n) >> 12) & 0xff) << AUD_CONFIG_UPPER_N_SHIFT) |	\
+	 (((n) & 0xfff) << AUD_CONFIG_LOWER_N_SHIFT))
 #define   AUD_CONFIG_PIXEL_CLOCK_HDMI_SHIFT	16
 #define   AUD_CONFIG_PIXEL_CLOCK_HDMI_MASK	(0xf << 16)
 #define   AUD_CONFIG_PIXEL_CLOCK_HDMI_25175	(0 << 16)