staging: kpc2000: kpc_i2c: Use devm_* API to manage mapped I/O space

The kpc_i2c 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 using the managed resource API.

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