omap3: overo: Set the Arbor43C 'expansionname'

The Gumstix Arbor43C expansion board [1] uses a customized device tree
file.  When this expansion board is detected, load this file.

[1] https://store.gumstix.com/index.php/products/635/Signed-off-by: NAsh Charles <ashcharles@gmail.com>

board/overo/overo.c

@@ -359,6 +359,7 @@ int misc_init_r(void)
 		MUX_GUMSTIX();
 		MUX_ARBOR43C();
 		setenv("defaultdisplay", "lcd43");
+		setenv("expansionname", "arbor43c");
 		break;
 	case ETTUS_USRP_E:
 		printf("Recognized Ettus Research USRP-E (rev %d %s)\n",