net: usb: make USB_RTL8153_ECM non user configurable

net: usb: make USB_RTL8153_ECM non user configurable

This refixes:

    commit 7da17624e7948d5d9660b910f8079d26d26ce453
    nt: usb: USB_RTL8153_ECM should not default to y

    In general, device drivers should not be enabled by default.

which basically broke the commit it claimed to fix, ie:

    commit 657bc1d10bfc23ac06d5d687ce45826c760744f9
    r8153_ecm: avoid to be prior to r8152 driver

    Avoid r8153_ecm is compiled as built-in, if r8152 driver is compiled
    as modules. Otherwise, the r8153_ecm would be used, even though the
    device is supported by r8152 driver.

this commit amounted to:

drivers/net/usb/Kconfig:

+config USB_RTL8153_ECM
+       tristate "RTL8153 ECM support"
+       depends on USB_NET_CDCETHER && (USB_RTL8152 || USB_RTL8152=n)
+       default y
+       help
+         This option supports ECM mode for RTL8153 ethernet adapter, when
+         CONFIG_USB_RTL8152 is not set, or the RTL8153 device is not
+         supported by r8152 driver.

drivers/net/usb/Makefile:

-obj-$(CONFIG_USB_NET_CDCETHER) += cdc_ether.o r8153_ecm.o
+obj-$(CONFIG_USB_NET_CDCETHER) += cdc_ether.o
+obj-$(CONFIG_USB_RTL8153_ECM)  += r8153_ecm.o

And as can be seen it pulls a piece of the cdc_ether driver out into
a separate config option to be able to make this piece modular in case
cdc_ether is builtin, while r8152 is modular.

While in general, device drivers should indeed not be enabled by default:
this isn't a device driver per say, but rather this is support code for
the CDCETHER (ECM) driver, and should thus be enabled if it is enabled.

See also email thread at:
  https://www.spinics.net/lists/netdev/msg767649.html

In:
  https://www.spinics.net/lists/netdev/msg768284.html

Jakub wrote:
  And when we say "removed" we can just hide it from what's prompted
  to the user (whatever such internal options are called)? I believe
  this way we don't bring back Marek's complaint.

Side note: these incorrect defaults will result in Android 13
on 5.15 GKI kernels lacking USB_RTL8153_ECM support while having
USB_NET_CDCETHER (luckily we also have USB_RTL8150 and USB_RTL8152,
so it's probably only an issue for very new RTL815x hardware with
no native 5.15 driver).

Fixes: 7da17624e7948d5d ("nt: usb: USB_RTL8153_ECM should not default to y")
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hayes Wang <hayeswang@realtek.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Link: https://lore.kernel.org/r/20220730230113.4138858-1-zenczykowski@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>