usb: common: rework CONFIG_USB_COMMON logic

The phy-am335x driver selects 'USB_COMMON', but all other drivers
use 'depends on' for that symbol, and it depends on USB || USB_GADGET
itself, which causes a Kconfig warning:

warning: (AM335X_PHY_USB) selects USB_COMMON which has unmet direct dependencies (USB_SUPPORT && (USB || USB_GADGET))

As suggested by Felipe Balbi, this turns the logic around, and makes
'USB_COMMON' selected by everything else that needs it, so we can
remove the dependencies.

Fixes: 59f042f644 ("usb: phy: phy-am335x: bypass first VBUS sensing for host-only mode")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Felipe Balbi <balbi@kernel.org>
Reviewed-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/phy/Kconfig

@@ -250,7 +250,8 @@ config PHY_SUN9I_USB
 	tristate "Allwinner sun9i SoC USB PHY driver"
 	depends on ARCH_SUNXI && HAS_IOMEM && OF
 	depends on RESET_CONTROLLER
-	depends on USB_COMMON
+	depends on USB_SUPPORT
+	select USB_COMMON
 	select GENERIC_PHY
 	help
 	  Enable this to support the transceiver that is part of Allwinner

drivers/usb/Kconfig

@@ -31,8 +31,6 @@ if USB_SUPPORT
 
 config USB_COMMON
 	tristate
-	default y
-	depends on USB || USB_GADGET
 
 config USB_ARCH_HAS_HCD
 	def_bool y
@@ -41,6 +39,7 @@ config USB_ARCH_HAS_HCD
 config USB
 	tristate "Support for Host-side USB"
 	depends on USB_ARCH_HAS_HCD
+	select USB_COMMON
 	select NLS  # for UTF-8 strings
 	---help---
 	  Universal Serial Bus (USB) is a specification for a serial bus

drivers/usb/gadget/Kconfig

@@ -15,6 +15,7 @@
 
 menuconfig USB_GADGET
 	tristate "USB Gadget Support"
+	select USB_COMMON
 	select NLS
 	help
 	   USB is a master/slave protocol, organized with one master