.buildkite: Increase timeout + jobs (DNM)

Increase timeout to allow testing completion on all impacted boards
Slightly Increase jobs as well

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
diff --git a/.buildkite/pipeline.yml b/.buildkite/pipeline.yml
index ebd3809..fcb9c85 100644
--- a/.buildkite/pipeline.yml
+++ b/.buildkite/pipeline.yml
@@ -4,8 +4,8 @@
     env:
       ZEPHYR_TOOLCHAIN_VARIANT: "zephyr"
       ZEPHYR_SDK_INSTALL_DIR: "/opt/toolchains/zephyr-sdk-0.12.4"
-    parallelism: 20
-    timeout_in_minutes: 180
+    parallelism: 25
+    timeout_in_minutes: 300
     retry:
       manual: true
     plugins: