omap: Beagle: only Cx boards use pin 23 for write protect

system_rev comes from u-boot and is a constant 0x20, so
Bx boards also fall in this 'if' and will get setup with the
wrong gpio_wp pin. Switch to using the Beagle revision routine
to correcly set pin 23 only for C1/2/3 and C4 Boards. Bx boards
will then use the correct default pin setting.
Signed-off-by: Robert Nelson <robertcnelson@gmail.com>
Acked-by: Jarkko Nikula <jhnikula@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/board-omap3beagle.c

@@ -272,7 +272,8 @@ static struct gpio_led gpio_leds[];
 static int beagle_twl_gpio_setup(struct device *dev,
 		unsigned gpio, unsigned ngpio)
 {
-	if (system_rev >= 0x20 && system_rev <= 0x34301000) {
+	if ((omap3_beagle_get_rev() == OMAP3BEAGLE_BOARD_C1_3) ||
+		(omap3_beagle_get_rev() == OMAP3BEAGLE_BOARD_C4)) {
 		omap_mux_init_gpio(23, OMAP_PIN_INPUT);
 		mmc[0].gpio_wp = 23;
 	} else {