build: fix kmod package build on non-GNU systems

BSD paste requires a filename argument, and it accepts - to use stdin as
intended.

Signed-off-by: Felix Fietkau <nbd@nbd.name>

include/kernel.mk

@@ -131,7 +131,7 @@ define ModuleAutoLoad
 	}; \
 	$(3) \
 	if [ -n "$$$$$$$$modules" ]; then \
-		modules="$$$$$$$$(echo "$$$$$$$$modules" | tr ' ' '\n' | sort | uniq | paste -s -d' ')"; \
+		modules="$$$$$$$$(echo "$$$$$$$$modules" | tr ' ' '\n' | sort | uniq | paste -s -d' ' -)"; \
 		mkdir -p $(2)/etc/modules.d; \
 		mkdir -p $(2)/CONTROL; \
 		echo "#!/bin/sh" > $(2)/CONTROL/postinst-pkg; \