feat(bl): adding psa crypto - crypto_mod_finish()

Adding call to crypto_mod_finish() at the end of crypto usage in the
bl mains. This is currently used for psa crytpo to destroy the
psa_key_ids in the psa key store, but could be expanded if required
later.

Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
Change-Id: I3dba9fe87b6bb64b629dda9d6c4653b116e7ee62
diff --git a/bl2/bl2_main.c b/bl2/bl2_main.c
index dbe9453..8ca7143 100644
--- a/bl2/bl2_main.c
+++ b/bl2/bl2_main.c
@@ -110,6 +110,8 @@
 	/* Teardown the Measured Boot backend */
 	bl2_plat_mboot_finish();
 
+	crypto_mod_finish();
+
 #if !BL2_RUNS_AT_EL3
 #ifndef __aarch64__
 	/*