omap-common: SPL: Add CONFIG_SPL_DISPLAY_PRINT / spl_display_print()

Only omap4/5 currently have a meaningful set of display text and overo
had been adding a function to display nothing.  Change how this works to
be opt-in and only turned on for omap4/5 now.

Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/arch/arm/cpu/armv7/omap-common/hwinit-common.c b/arch/arm/cpu/armv7/omap-common/hwinit-common.c
index 459ebb5..4d7ef5c 100644
--- a/arch/arm/cpu/armv7/omap-common/hwinit-common.c
+++ b/arch/arm/cpu/armv7/omap-common/hwinit-common.c
@@ -92,6 +92,11 @@
 {
 	boot_params_ptr = (u32 *) &boot_params;
 }
+
+void spl_display_print(void)
+{
+	omap_rev_string();
+}
 #endif
 
 /*
diff --git a/arch/arm/cpu/armv7/omap-common/spl.c b/arch/arm/cpu/armv7/omap-common/spl.c
index 4d1ac85..b10832a 100644
--- a/arch/arm/cpu/armv7/omap-common/spl.c
+++ b/arch/arm/cpu/armv7/omap-common/spl.c
@@ -219,10 +219,7 @@
 
 	printf("\nU-Boot SPL %s (%s - %s)\n", u_boot_rev, U_BOOT_DATE,
 		U_BOOT_TIME);
-	omap_rev_string();
-}
-
-void __weak omap_rev_string()
-{
-	printf("Texas Instruments Revision detection unimplemented\n");
+#ifdef CONFIG_SPL_DISPLAY_PRINT
+	spl_display_print();
+#endif
 }