staging: kpc2000: kpc_spi: use devm_* API to manage mapped I/O space

The kpc_spi driver does not unmap its I/O space upon error cases in the
probe() function or upon remove(). Make the driver clean up after itself
more maintainably by migrating to using the managed resource API.

Signed-off-by: Geordan Neukum <gneukum1@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>