ibm: tacoma: Fix I2C hwmon conf files paths

The AST2600 device tree paths for the I2C buses are different than on
the AST2500, so add a new set of hwmon conf files for the tacoma system
that are the same as witherspoon but just in a different directory.

Stopped doing CHIPS_append in the recipe since witherspoon-tacoma
inherits from witherspoon it was getting all of witherspoon's conf files
as well.

(From meta-ibm rev: b9cd483488901d6d379360317caf537fa4529f90)

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I29c61d541e58cd0113caf8584d2e5720b738d090
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>