omap3: evm: Fixes for CONFIG_NAND, SPL_OS_BOOT, USB, and environment

- Pass MTDPARTS kernel arguments to kernel
- Use Kconfig CONFIG_NAND instead of CONFIG_SYS_EXTRA_OPTIONS="NAND"
- Call 'usb_stop' on kernel start
- Update Falcon mode setup to match other OMAP3 boards
- Use "uEnv.txt" as boot script instead of "boot.scr"
diff --git a/board/ti/evm/evm.c b/board/ti/evm/evm.c
index 6bf57f9..1f0433d 100644
--- a/board/ti/evm/evm.c
+++ b/board/ti/evm/evm.c
@@ -122,6 +122,17 @@
 	return 0;
 }
 
+#if defined(CONFIG_SPL_OS_BOOT)
+int spl_start_uboot(void)
+{
+	/* break into full u-boot on 'c' */
+	if (serial_tstc() && serial_getc() == 'c')
+		return 1;
+
+	return 0;
+}
+#endif /* CONFIG_SPL_OS_BOOT */
+
 #if defined(CONFIG_SPL_BUILD)
 /*
  * Routine: get_board_mem_timings
@@ -323,7 +334,14 @@
 }
 #endif /* CONFIG_MMC */
 
-#if defined(CONFIG_USB_EHCI_HCD)
+#if defined(CONFIG_USB_EHCI_HCD) && !defined(CONFIG_SPL_BUILD)
+/* Call usb_stop() before starting the kernel */
+void show_boot_progress(int val)
+{
+	if (val == BOOTSTAGE_ID_RUN_OS)
+		usb_stop();
+}
+
 static struct omap_usbhs_board_data usbhs_bdata = {
 	.port_mode[0] = OMAP_USBHS_PORT_MODE_UNUSED,
 	.port_mode[1] = OMAP_EHCI_PORT_MODE_PHY,