Fix below warnings that only generate for a 64 bit system:
greybus/svc.c:202:16: warning: format ‘%d’ expects argument of type ‘int’, but argument 4 has type ‘size_t {aka long unsigned int}’ [-Wformat=]
dev_err(dev, "%s: Illegal size of hello request (%d %d)\n",
^
greybus/svc.c:202:16: warning: format ‘%d’ expects argument of type ‘int’, but argument 5 has type ‘long unsigned int’ [-Wformat=]