tools: tfm_parse_manifest_list: Fix undefined reference to SLIH API

Fix undefined reference to SLIP API e.g. psa_eoi when creating a
partition that listens to multiple interrupt sources using both FLIH and
SLIH interrupt handling.
Since the FLIH interrupt count is more than 1 the SLIH API is excluded
due to the elif check.

Change-Id: I23b7a699449963d3d43e45b06f223c4d7b172431
Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>
diff --git a/tools/tfm_parse_manifest_list.py b/tools/tfm_parse_manifest_list.py
index baf136b..ce7bb60 100644
--- a/tools/tfm_parse_manifest_list.py
+++ b/tools/tfm_parse_manifest_list.py
@@ -423,7 +423,7 @@
 
     if partition_statistics['flih_num'] > 0:
         config_impl['CONFIG_TFM_FLIH_API'] = 1
-    elif partition_statistics['slih_num'] > 0:
+    if partition_statistics['slih_num'] > 0:
         config_impl['CONFIG_TFM_SLIH_API'] = 1
 
     context['partitions'] = partition_list