platform/chrome: Make i2c_adapter_names static

Not used outside of the file, so declaration should be static. Picked up by
sparse:

drivers/platform/chrome/chromeos_laptop.c:44:12: warning: symbol
    'i2c_adapter_names' was not declared. Should it be static?
Signed-off-by: Olof Johansson <olof@lixom.net>
Reviewed-by: Benson Leung <bleung@chromium.org>

drivers/platform/chrome/chromeos_laptop.c

@@ -41,7 +41,7 @@ static struct i2c_client *als;
 static struct i2c_client *tp;
 static struct i2c_client *ts;
 
-const char *i2c_adapter_names[] = {
+static const char *i2c_adapter_names[] = {
 	"SMBus I801 adapter",
 	"i915 gmbus vga",
 	"i915 gmbus panel",