ipmi_si: Change ipmi_si_add_smi() to take just I/O info

Instead of allocating the smi_info structure, filling in the I/O
info, and passing it to ipmi_si_add_smi(), just pass the I/O
info in the io structure and let ipmi_si_add_smi() allocate
the smi_info structure.

This required redoing the way the remove functions for some
device interfaces worked, a new function named
ipmi_si_remove_by_dev() allows the device to be passed in and
detected instead of using driver data, which couldn't be
filled out easily othersize.

After this the platform handling should be decoupled from the
smi_info structure and that handling can be pulled out to its
own files.

Signed-off-by: Corey Minyard <cminyard@mvista.com>