Added options for an internal SD card to be handled by recovery.

Exable uses in BoardConfig.mk:
	BOARD_HAS_SDCARD_INTERNAL := true
	BOARD_SDCARD_DEVICE_INTERNAL := /dev/block/mmcblk3p1

Setting BOARD_SDCARD_DEVICE_SECONDARY to the same value as
	BOARD_SDCARD_DEVICE_INTERNAL will allow the device to
	"fall back" to the internal SD card for other actions.

Change-Id: I2cf8ab4b1d385ac714f5b7416b915d059033d94b
diff --git a/roots.h b/roots.h
index 02ec2fb..833c1b5 100644
--- a/roots.h
+++ b/roots.h
@@ -37,6 +37,10 @@
 #define BOARD_SDCARD_DEVICE_SECONDARY "/dev/block/mmcblk0"
 #endif
 
+#ifndef BOARD_SDCARD_DEVICE_INTERNAL
+#define BOARD_SDCARD_DEVICE_INTERNAL g_default_device
+#endif
+
 #ifndef BOARD_SDEXT_DEVICE
 #define BOARD_SDEXT_DEVICE "/dev/block/mmcblk0p2"
 #endif