mkbp_event,include/config.h: Clarify MKBP delivery method.

Now we have two MKBP delivery methods:
1. define CONFIG_MKBP_USE_HOST_EVENT to notify via host event
2. undef CONFIG_MKBP_USE_HOST_EVENT to notify via GPIO interrupt

It may become more complicated if new notification methods introduced.
e.g.: mt_scp uses IPI, rather than host event and GPIO interrupt.
This CL does:
1. add CONFIG_MKBP_USE_GPIO to explicilty declare that MKBP event are
   sent via GPIO interrupt.
2. CONFIG_MKBP_USE_CUSTOM for boards which have custmized methods.
3. Remove weak attribute in mkbp_set_host_active (which can be done
   with CONFIG_MKBP_USE_CUSTOM now.
4. Removes mkbp_set_host_active function in board Nocturne.  It only
   deliver MKBP events through GPIO interrupt now.

BRANCH=None
BUG=b:120808999
TEST=grep -rn "CONFIG_MKBP_USE_GPIO\|EC_INT_L" board/ baseboard/ and
     see the result is reasonable:
     1. EC_INT_L must be 1-to-1 mapped to define CONFIG_MKBP_USE_GPIO in
        every board, except that meep, yorp, ampton which are defined in
        baseboard octopus.
     2. undef CONFIG_MKBP_USE_GPIO in bip and casta, which use host
        event, but also have baseboard octopus.

Change-Id: I4af6110e4fd3c009968075c3623ef2d91cbd770b
Signed-off-by: Yilun Lin <yllin@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1490794
Commit-Ready: Jett Rink <jettrink@chromium.org>
Tested-by: Yilun Lin <yllin@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-by: Jett Rink <jettrink@chromium.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/mkbp_event.h b/include/mkbp_event.h
index 61eb2c9052..c1f3a238dc 100644
--- a/include/mkbp_event.h
+++ b/include/mkbp_event.h
@@ -58,6 +58,13 @@ void mkbp_set_host_active_via_gpio(int active);
 void mkbp_set_host_active_via_event(int active);
 
 /*
+ * Communicate an MKBP event to the AP via custom method.
+ *
+ * This can be used if a board has a custom method.
+ */
+void mkbp_set_host_active_via_custom(int active);
+
+/*
  * The struct to store the event source definition.  The get_data routine is
  * responsible for returning the event data when queried by the AP.  The
  * parameter 'data' points to where the event data needs to be stored, and