mfd: lpc_ich: Staticize struct 'lpc_chipset_info'

'lpc_chipset_info' is used only in this file.

Fix the following sparse warning:

drivers/mfd/lpc_ich.c:216:21: warning: symbol 'lpc_chipset_info' was not declared. Should it be static?

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>