xhci: incorrect variable type of remain in case of short xfer

[Takahiro HAYASHI]

Hello,

In function xhci_event_xfer() of sys/dev/usb/xhci.c at line 717
the variable 'remain' is declared as uint8_t, but it should be
uint32_t as TRB_REMAIN has 24 bits width.


Thanks,
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