platform/chrome: cros_ec_proto: add Kunit test for getting cmd mask error

cros_ec_query_all() uses cros_ec_get_host_command_version_mask() to
query the supported MKBP version; cros_ec_get_host_command_version_mask()
uses send_command() for transferring the host command.

Returning >=0 from send_command() only denotes the transfer was success.
cros_ec_get_host_command_version_mask() should check if EC wasn't happy
by checking `msg->result`.

Add a Kunit test for returning error in `msg->result` in
cros_ec_get_host_command_version_mask().  For the case,
cros_ec_query_all() should find the EC device doesn't support MKBP.

Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20220609084957.3684698-16-tzungbi@kernel.org