All sensors should return a target speed value

All tach sensors associated with a fan should return a target speed
sensor from its getTarget function. In the case where a target speed
sensor does not exist for the tach sensor, it retrieves and returns the
target speed value from the fan where the fan finds the target speed
value from a tach sensor the fan contains that provides it.

Resolves openbmc/openbmc#2784

Change-Id: Iea5561b0aad6942be52af262c7255c60e5e75c7a
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
4 files changed