tf-m-split-build: Directly trigger build-and-test job

To make tf-m-split-build job more flexible to verify TF-M split build
feature, change this job to directly trigger build-and-test job so that
it is able to manually trigger test with specific config groups.

Signed-off-by: Xinyu Zhang <xinyu.zhang@arm.com>
Change-Id: I38500fccdec0de0361a2329cb141d56d63597d94
1 file changed