usb: typec: ucsi: Only set number of plug altmodes after registration

Move the setting of the plug's number of alternate modes into the
same condition as the plug's registration to prevent dereferencing the
connector's plug pointer while it is null.

Fixes: c313a44a ("usb: typec: ucsi: Always set number of alternate modes")
Suggested-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Jameson Thies <jthies@google.com>
Reviewed-by: Benson Leung <bleung@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Link: https://lore.kernel.org/r/20240625004607.3223757-1-jthies@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>