usb: usb-skeleton: Update min() to min_t()

This patch fixes the checkpatch.pl warning:
WARNING: min() should probably be min_t(size_t, count, MAX_TRANSFER)
+	size_t writesize = min(count, (size_t)MAX_TRANSFER);

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/20210922212037.GA8110@matrix-ESPRIMO-P710


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