thunderbolt: Introduce usb4_port_sb_opcode_err_to_errno() helper

The usb4_port_sb_opcode_err_to_errno() converts from USB4 error codes
to the Linux errno space. In particular, this makes the intention
of the repeating usb4_port_retimer_read() call in the
usb4_port_retimer_nvm_authenticate_status() clearer.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>