usb: ehci: replace scnprintf() with sysfs_emit()

usb: ehci: replace scnprintf() with sysfs_emit()

Per Documentation/filesystems/sysfs.rst, show() methods should only
use sysfs_emit() or sysfs_emit_at() when formatting values to be
returned to userspace.

Convert the uses of scnprintf() in sysfs show() methods to
sysfs_emit() and sysfs_emit_at() for better safety and consistency.

Signed-off-by: Hendrik Hamerlinck <hendrik.hamerlinck@hammernet.be>
Link: https://lore.kernel.org/r/20250623140950.61568-1-hendrik.hamerlinck@hammernet.be
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>