usb: host: ehci-q: make qtd_fill() return *unsigned int*

usb: host: ehci-q: make qtd_fill() return *unsigned int*

At the end of qtd_fill(), we assign the 'int count' variable to the 'size_t
length' field of 'struct ehci_qtd' -- which implies a problematic type cast.
Let's make that variable and the function's result *unsigned int* instead...

Found by Linux Verification Center (linuxtesting.org) with the SVACE static
analysis tool.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Link: https://lore.kernel.org/r/8c64fdeb-5857-8cb3-cfd8-0c248a14b909@omp.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>