ARM: OMAP2+: Configure voltage controller for retention

Similar to existing omap3_vc_set_pmic_signaling(), let's add omap4
specific omap4_vc_set_pmic_signaling(). This allows the configured
devices to enable voltage controller for retention later on during
init.

Cc: Merlijn Wajer <merlijn@wizzup.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
diff --git a/arch/arm/mach-omap2/vc.h b/arch/arm/mach-omap2/vc.h
index 5bf0886..9e861db 100644
--- a/arch/arm/mach-omap2/vc.h
+++ b/arch/arm/mach-omap2/vc.h
@@ -117,7 +117,7 @@ extern struct omap_vc_param omap4_iva_vc_data;
 extern struct omap_vc_param omap4_core_vc_data;
 
 void omap3_vc_set_pmic_signaling(int core_next_state);
-
+void omap4_vc_set_pmic_signaling(int core_next_state);
 
 void omap_vc_init_channel(struct voltagedomain *voltdm);
 int omap_vc_pre_scale(struct voltagedomain *voltdm,