usb: gadget: Move CONFIG_USB_GADGET_VBUS_DRAW to Kconfig

The description was borrowed from kernel. Definitions were added to
defconfig files in a way that "make savedefconfig" generates exactly
the same file as used defconfig.

Boards using 0 mA as CONFIG_USB_GADGET_VBUS_DRAW value were moved to use
2 mA (as minimal allowed by Kconfig).

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
diff --git a/include/configs/am43xx_evm.h b/include/configs/am43xx_evm.h
index fd3f6a7..0dd9c7a7 100644
--- a/include/configs/am43xx_evm.h
+++ b/include/configs/am43xx_evm.h
@@ -122,6 +122,10 @@
 #endif
 
 /* USB GADGET */
+#if defined(CONFIG_SPL_BUILD) && !defined(CONFIG_SPL_USBETH_SUPPORT)
+#undef CONFIG_USB_GADGET_VBUS_DRAW
+#endif
+
 #if !defined(CONFIG_SPL_BUILD) || \
 	(defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_USBETH_SUPPORT))
 #define CONFIG_USB_DWC3_PHY_OMAP
@@ -130,7 +134,6 @@
 #define CONFIG_USB_DWC3_GADGET
 
 #define CONFIG_USB_GADGET_DOWNLOAD
-#define CONFIG_USB_GADGET_VBUS_DRAW 2
 #define CONFIG_G_DNL_MANUFACTURER "Texas Instruments"
 #define CONFIG_G_DNL_VENDOR_NUM 0x0403
 #define CONFIG_G_DNL_PRODUCT_NUM 0xBD00