ssl: fix included pk header file

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index f9a4767..549162c 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -55,7 +55,7 @@
 #include "mbedtls/ecjpake.h"
 #endif
 
-#include "pk_wrap.h"
+#include "mbedtls/pk.h"
 #include "common.h"
 
 /* Shorthand for restartable ECC */