USB: whci-hcd: fix type and format warnings in sg code

Fix type and format warning in the new sg code.  Remove the very chatty
debug messages that were left in by mistake and use min_t() as required
(no one seems to agree on a type for buffer sizes).

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>