gpio/omap: cleanup show revision, remove cpu_is checks, display only once

Remove cpu_is_* checks from gpio_show_revision() by passing in the
revision address offset from platform data.  SoCs with no revision
register (15xx, 7xx, and all MPUIOs) use -1 (actually, USHRT_MAX) to
signify no register.

While here, all GPIO banks are assumed to be the same revision, so fix
show_revision() to only show the revision for the first bank it finds.
This removes duplicate GPIO revision prints during boot.

Thanks to Charulatha V <charu@ti.com> for finding/fixing a few -1s
that were missed in the original patch.

Signed-off-by: Kevin Hilman <khilman@ti.com>
diff --git a/arch/arm/plat-omap/include/plat/gpio.h b/arch/arm/plat-omap/include/plat/gpio.h
index 7a3f067..91e8de3 100644
--- a/arch/arm/plat-omap/include/plat/gpio.h
+++ b/arch/arm/plat-omap/include/plat/gpio.h
@@ -175,6 +175,7 @@
 };
 
 struct omap_gpio_reg_offs {
+	u16 revision;
 	u16 direction;
 	u16 datain;
 	u16 dataout;