platform/chrome: cros_ec_lpc: MEC access can use an AML mutex

Framework Laptops have ACPI code which accesses the MEC memory. It
uses an AML mutex to prevent concurrent access. But the cros_ec_lpc
driver was not aware of this mutex. The ACPI code and LPC driver both
attempted to talk to the EC at the same time, messing up communication
with the EC.

Allow the LPC driver MEC code to find and use the AML mutex.

Tested-by: Dustin L. Howett <dustin@howett.net>
Signed-off-by: Ben Walsh <ben@jubnut.com>
Link: https://lore.kernel.org/r/20240605063351.14836-3-ben@jubnut.com


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