Some drivers follow this convention (lm63, lm83, lm90, smsc47m192).
However some drivers omit the "input" part and create files named
fan1_fault (pc87427) or temp1_fault (dme1737). And the new "generic"
libsensors follows this second (non-standard) convention, so it fails
to report fault conditions for drivers which follow the standard.
We want a single naming scheme, and everyone seems to prefer the
shorter variant, so let's go for it.