Update chromeec submodule to upstream master

Updating from commit id a1afae4:
2019-10-02 11:47:45 +0000 - (juniper: initial setup)

to commit id a2390f3:
2020-12-01 08:35:44 +0000 - (servo_v4/usb_pd_policy: Reject SNK->SRC power swap if CC_ALLOW_SRC not set)

This brings in 4022 new commits.

Change-Id: Ib13921aa78a60f88455223eff602296abc424ca8
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48212
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/3rdparty/chromeec b/3rdparty/chromeec
index a1afae4..a2390f3 160000
--- a/3rdparty/chromeec
+++ b/3rdparty/chromeec
@@ -1 +1 @@
-Subproject commit a1afae4e002a3eccd7835ac898259b0690e9e61a
+Subproject commit a2390f3c505a4684535c08da27736099a63850fe