platform/chrome: cros_ec_lpc: Move mec_init to device probe

Disregarding the weird global state hiding in this cros_ec_lpc_mec_*()
stuff, it belongs in device probe. We shouldn't assume we can access
hardware resources when the device isn't attached to the driver.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20221101152132.v2.1.I0728421299079b104710c202d5d7095b2674fd8c@changeid