Support .sealing_key3 in privileged compartments

sdk/privileged-compartment.ldscript

diff --git a/sdk/privileged-compartment.ldscript b/sdk/privileged-compartment.ldscript
index c8f1b0a..ba0fdef 100644
--- a/sdk/privileged-compartment.ldscript
+++ b/sdk/privileged-compartment.ldscript
@@ -25,6 +25,7 @@
 		# The sealing keys for this compartment is before the import table, if they exist
 		*(.sealing_key1*)
 		*(.sealing_key2*)
+		*(.sealing_key3*)
 	}
 	# Lay out the compartment imports section.  This will end up on PCC.
 	.compartment_import_table : ALIGN(8)