fix(coverity): enable SDEI support for imx8mn builds

Moreover, modify the default config for imx8mn build to enable
SDEI support.

Also, update the exclusion list to include the oem_svc.c file
which is no more used by any upstream platform.

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: I59793d81f7aa71a36a3de56ef8f58f25cd7ae4ef
diff --git a/script/tf-coverity/tf-cov-make b/script/tf-coverity/tf-cov-make
index f55411e..cd4b89e 100755
--- a/script/tf-coverity/tf-cov-make
+++ b/script/tf-coverity/tf-cov-make
@@ -373,7 +373,7 @@
     $(common_flags) all
 make PLAT=imx8mm $(common_flags) NEED_BL2=yes MEASURED_BOOT=1 \
     TPM_HASH_ALG=sha256 ${TBB_OPTIONS} all
-make PLAT=imx8mn $(common_flags) all
+make PLAT=imx8mn $(common_flags) SDEI_SUPPORT=1 all
 make PLAT=imx8mp $(common_flags) NEED_BL2=yes ${TBB_OPTIONS} all
 
 # Due to the limited OCRAM space that can be used for TF-A, build test