libsel4utils: Add headers for IRQ server sources

These new headers are necessary for the refactoring of the IRQ server.

libsel4utils/src/irq_server/irq_server.c

diff --git a/libsel4utils/src/irq_server/irq_server.c b/libsel4utils/src/irq_server/irq_server.c
index dd256d1..d6f42c7 100644
--- a/libsel4utils/src/irq_server/irq_server.c
+++ b/libsel4utils/src/irq_server/irq_server.c
@@ -12,11 +12,14 @@
 
 #include <sel4utils/irq_server.h>
 
+#include <errno.h>
 #include <simple/simple.h>
 #include <sel4utils/thread.h>
 #include <vka/capops.h>
 #include <stdlib.h>
 #include <string.h>
+#include <platsupport/irq.h>
+#include <sel4platsupport/irq.h>
 
 #include <utils/util.h>