mb/google/nissa/var/riven: Add GPIO table

Refer to the reference board of nivviks, and update GPIO settings
based on latest schematic (Riven(ZDK)_MB_Proto_0601.pdf).

BUG=b:337169542
TEST=Local build successfully.

Change-Id: Ic43c743fcc2ec89b5a9e2fbe1a87b833d59f1e74
Signed-off-by: David Wu <david_wu@quanta.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/82973
Reviewed-by: Subrata Banik <subratabanik@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/google/brya/variants/riven/Makefile.mk b/src/mainboard/google/brya/variants/riven/Makefile.mk
new file mode 100644
index 0000000..d38141c
--- /dev/null
+++ b/src/mainboard/google/brya/variants/riven/Makefile.mk
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+bootblock-y += gpio.c
+
+romstage-y += gpio.c
+
+ramstage-y += gpio.c