drivers: remove the SGI SN2 IOC4 base support

The IOC4 is a multi-function chip seen on SGI SN2 and some SGI MIPS
systems.  This removes the base driver, which while not having an SN2
Kconfig dependency was only for sub-drivers that had one.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lkml.kernel.org/r/20190813072514.23299-15-hch@lst.de


Signed-off-by: Tony Luck <tony.luck@intel.com>