wspoon: Update fan pres I2C path for 5.0 kernel

In the 5.0 Linux kernel, an I2C device path segment changed:
    i2c@1e78a000 -> bus@1e78a000

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I6aa0cb5ca84f9d0f6a7c563313951527c97b3319
1 file changed