usb: typec: Remove alt->adev.dev.class assignment

The typec plug alternate mode is already registered as part of the bus.
When both class and bus are set for a device, device_add() attempts to
create the "subsystem" symlink in the device's sysfs directory twice, once
for the bus and once for the class.
This results in a duplicate filename error during registration,
causing the alternate mode registration to fail with warnings:

cannot create duplicate filename '/devices/pci0000:00/0000:00:1f.0/
PNP0C09:00/GOOG0004:00/cros-ec-dev.1.auto/cros_ec_ucsi.3.auto/typec/
port1/port1-cable/port1-plug0/port1-plug0.0/subsystem'
typec port0-plug0: failed to register alternate mode (-17)
cros_ec_ucsi.3.auto: failed to registers svid 0x8087 mode 1

Cc: stable <stable@kernel.org>
Fixes: 67ab45426215 ("usb: typec: Set the bus also for the port and plug altmodes")
Tested-by: Madhu M <madhu.m@intel.corp-partner.google.com>
Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Benson Leung <bleung@chromium.org>
Link: https://patch.msgid.link/20260324102903.1416210-1-akuchynski@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>