usb: xhci: move untargeted transfer event handling to a separate function

usb: xhci: move untargeted transfer event handling to a separate function

Move handling transfer events without a target transfer TRB into
handle_transferless_tx_event(), this type of event does not utilize the
rest of handle_tx_event() and as a result it's better to separate it
into a dedicated function.

Additionally, this change reduces handle_tx_event()'s size and makes it
more readable.

[Mathias: Simplify code to return helper function value directly. This
removes the second xhci_err() message for untargeted and unexpected
event completion types]

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20240626124835.1023046-12-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>