net: use common rand()/srand() functions

Replace rand() with the functions from lib/. The link-local network code
stores its own seed, derived from the MAC address. Thus making it
independent from calls to srand() in other modules.

Signed-off-by: Michael Walle <michael@walle.cc>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/lib/Makefile b/lib/Makefile
index 0ca45fc..556601c 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -67,8 +67,10 @@
 COBJS-$(CONFIG_BOOTP_PXE) += uuid.o
 COBJS-y += vsprintf.o
 COBJS-$(CONFIG_RANDOM_MACADDR) += rand.o
+COBJS-$(CONFIG_BOOTP_RANDOM_DELAY) += rand.o
+COBJS-$(CONFIG_CMD_LINK_LOCAL) += rand.o
 
-COBJS	:= $(COBJS-y)
+COBJS	:= $(sort $(COBJS-y))
 SRCS	:= $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(COBJS))