drm/i915: Extend gpio read/write to other cores

Make the gpio read/write functions more generic iosf sideband read/write
functions, taking the iosf port as argument.

v2: rebase
v3: rebase
v4 by Jani: address Ville's review
v5 by Jani: drop the PCI_DEVFN change (Ville)

Signed-off-by: Deepak M <m.deepak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1454604915-17142-1-git-send-email-jani.nikula@intel.com
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index bd126ff..8216665 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3471,8 +3471,8 @@
 u32 vlv_punit_read(struct drm_i915_private *dev_priv, u32 addr);
 void vlv_punit_write(struct drm_i915_private *dev_priv, u32 addr, u32 val);
 u32 vlv_nc_read(struct drm_i915_private *dev_priv, u8 addr);
-u32 vlv_gpio_nc_read(struct drm_i915_private *dev_priv, u32 reg);
-void vlv_gpio_nc_write(struct drm_i915_private *dev_priv, u32 reg, u32 val);
+u32 vlv_iosf_sb_read(struct drm_i915_private *dev_priv, u8 port, u32 reg);
+void vlv_iosf_sb_write(struct drm_i915_private *dev_priv, u8 port, u32 reg, u32 val);
 u32 vlv_cck_read(struct drm_i915_private *dev_priv, u32 reg);
 void vlv_cck_write(struct drm_i915_private *dev_priv, u32 reg, u32 val);
 u32 vlv_ccu_read(struct drm_i915_private *dev_priv, u32 reg);