drivers/net/ne2k: Make it work for bootblock

This code was written in a romcc bootblock time. There is no reason why
it would not work in bootblock now.

Untested but expected to work.

Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Change-Id: I708e8a3b503eb3a7fdf6063803d666529096f651
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78934
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@gmail.com>

src/lib/Makefile.inc

@@ -116,6 +116,7 @@ ramstage-y += rtc.c
 romstage-$(CONFIG_COLLECT_TIMESTAMPS) += timestamp.c
 romstage-$(CONFIG_CONSOLE_CBMEM) += cbmem_console.c
 
+bootblock-y += compute_ip_checksum.c
 romstage-y += compute_ip_checksum.c
 romstage-y += dimm_info_util.c
 ifeq ($(CONFIG_COMPILER_GCC),y)