spl: support for booting via usbeth

In case of usbeth booting just call net_load_image("usb_ether").
This patch also adds CONFIG_SPL_USBETH_SUPPORT and
CONFIG_SPL_MUSB_NEW_SUPPORT config options to enable linking of SPL
against USB gagdet support and new MUSB driver resp.
Signed-off-by: NIlya Yanok <ilya.yanok@cogentembedded.com>

common/spl/spl.c

@@ -220,6 +220,11 @@ void board_init_r(gd_t *dummy1, ulong dummy2)
 		spl_net_load_image(NULL);
 #endif
 		break;
+#endif
+#ifdef CONFIG_SPL_USBETH_SUPPORT
+	case BOOT_DEVICE_USBETH:
+		spl_net_load_image("usb_ether");
+		break;
 #endif
 	default:
 		debug("SPL: Un-supported Boot Device\n");

spl/Makefile

@@ -81,6 +81,8 @@ LIBS-$(CONFIG_SPL_POST_MEM_SUPPORT) += post/drivers/memory.o
 LIBS-$(CONFIG_SPL_NET_SUPPORT) += net/libnet.o
 LIBS-$(CONFIG_SPL_ETH_SUPPORT) += drivers/net/libnet.o
 LIBS-$(CONFIG_SPL_ETH_SUPPORT) += drivers/net/phy/libphy.o
+LIBS-$(CONFIG_SPL_MUSB_NEW_SUPPORT) += drivers/usb/musb-new/libusb_musb-new.o
+LIBS-$(CONFIG_SPL_USBETH_SUPPORT) += drivers/usb/gadget/libusb_gadget.o
 
 ifneq ($(CONFIG_AM33XX)$(CONFIG_OMAP34XX)$(CONFIG_OMAP44XX)$(CONFIG_OMAP54XX),)
 LIBS-y += $(CPUDIR)/omap-common/libomap-common.o