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/tf_config/imx8mn-default b/tf_config/imx8mn-sdei
similarity index 74%
rename from tf_config/imx8mn-default
rename to tf_config/imx8mn-sdei
index 66391c6..361316f 100644
--- a/tf_config/imx8mn-default
+++ b/tf_config/imx8mn-sdei
@@ -1,2 +1,3 @@
 CROSS_COMPILE=aarch64-none-elf-
 PLAT=imx8mn
+SDEI_SUPPORT=1