platform/chrome: cros_ec_lpc: Support direct EC register memory access

Add support to access EC memory region HOST command and ACPI memory
region directly.

The memory region comes from the CRS ACPI resource descriptor.

The driver retrieves the memory information by adding a resource walker
for the CRS region. If a memory region is found, it is mapped and the
driver uses a new set of read/write primitives to access the EC doorbell
and external registers.

Once the memory is mapped, it belongs to the driver:
grep GOOG0004 /proc/iomem
    fe0b0000-fe0bffff : GOOG0004:00

We can verify the communication is established checking the EC version,
or monitoring the commands using the cros-ec kernel tracer.

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Link: https://lore.kernel.org/r/20250107174514.2748108-3-gwendal@chromium.org


Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>