kconfig: subsys: usb: Remove redundant USB_DEVICE_STACK deps.

subsys/usb/Kconfig 'source's subsys/usb/class/Kconfig (which in turn
'source's subsys/usb/class/netusb/Kconfig) within an
'if USB_DEVICE_STACK', so the dependencies on USB_DEVICE_STACK added
within those files are redundant.

'if FOO' is just shorthand for adding 'depends on FOO' to each item
within the 'if'. Dependencies on menus work similarly. There are no
"conditional includes" in Kconfig, so 'if FOO' has no special meaning
around a source. Conditional includes wouldn't be possible, because an
if condition could include (directly or indirectly) forward references
to symbols not defined yet.

Tip: When adding a symbol, check its dependencies in the menuconfig
('ninja menuconfig', then / to jump to the symbol). The menuconfig also
shows how the file with the symbol got included, so if you see
duplicated dependencies, it's easy to hunt down where they come from.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>

subsys/usb/class/Kconfig

@@ -6,8 +6,6 @@
 # SPDX-License-Identifier: Apache-2.0
 #
 
-if USB_DEVICE_STACK
-
 config USB_CDC_ACM
 	bool "USB CDC ACM Device Class Driver"
 	select SERIAL_HAS_DRIVER
@@ -147,5 +145,3 @@ config USB_DFU_DETACH_TIMEOUT
 	int
 	depends on USB_DFU_CLASS
 	default 1000
-
-endif # CONFIG_USB_DEVICE_STACK

subsys/usb/class/netusb/Kconfig

@@ -7,7 +7,6 @@
 #
 
 menu "USB Device Networking support"
-	depends on USB_DEVICE_STACK
 
 config USB_DEVICE_NETWORK
 	bool