Bug#534413: hw-detect: should not rely on testing for /proc/bus/usb

[Frans Pop <elendil@planet.nl>]

Package: hw-detect
Version: 1.72
Severity: important

In hw-detect.sh there are two locations where the script checks if
/sys/bus/usb exists, but usbfs will no longer be available in kernel 
2.6.31, so another method will need to be found.

Possibly a test for /sys/bus/usb/devices/ can be used instead. It does not 
exist if no USB drivers are loaded and will be empty if drivers are 
loaded but no devices (buses) are present.