mfd: lpc_ich: One uninitialized cell is no error

At every boot of an (outdated) laptop lpc_ich prints an error:
    lpc_ich 0000:00:1f.0: I/O space for GPIO uninitialized

But if one looks at lpc_ich's probe function one notices that the code
only cares if both lpc_ich_init_wdt() and lpc_ich_init_gpio() fail to
add any cells. So stop treating the failure to add a single cell as an
error. Those messages can be printed at notice level. And then only warn
if no cells were added.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>