usb: host: ehci-dbg: use scnprintf() in qh_lines()

This patch replaces two snprintf() calls with scnprintf() in qh_lines()
and hence removes the unneeded sequential truncation tests.

Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>