staging: lustre: ptlrpc: add missing include directive

Without including ptlrpc_internal.h, GCC gives prototype warnings
"pack_generic.c:642:5: warning: no previous prototype for ..."
and sparse also complains "pack_generic.c:642:5: warning: symbol
'lustre_unpack_req_ptlrpc_body' was not declared. ..."
Signed-off-by: Ioan-Adrian Ratiu <adi@adirat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/ptlrpc/pack_generic.c

@@ -52,6 +52,8 @@
 #include "../include/obd_cksum.h"
 #include "../include/lustre/ll_fiemap.h"
 
+#include "ptlrpc_internal.h"
+
 static inline int lustre_msg_hdr_size_v2(int count)
 {
 	return cfs_size_round(offsetof(struct lustre_msg_v2,