fix: update field name for bus path disk selector

[smira]

s/buspath/bus_path/.

[smira]

/m

[ammmze]

Does this happen to fix this error I receive when doing a talosctl validate on a config that contains an install disk busPath?

2 errors occurred:
        * install disk selector is invalid: ERROR: <input>:-1:0: undefined field 'buspath'
        * either install disk or diskSelector should be defined