nvramcui: Add Makefile

Users had to build nvramcui manually because payload.sh was only meant
for abuild. Now the user can build it with:
  cd payloads/libpayload/ && make menuconfig && make && make install
  cd ../nvramcui && make

Change-Id: I409a3c39a1e1738e8071febb1a3f169e1aee959a
Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@no-log.org>
Reviewed-on: https://review.coreboot.org/13778
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

payloads/nvramcui/Makefile

@@ -0,0 +1,10 @@
+LPGCC = ../libpayload/install/libpayload/bin/lpgcc
+
+all: nvramcui.elf
+
+%.elf:
+	$(LPGCC) -o $*.elf $*.c
+
+.PHONY:
+clean:
+	rm -f nvramcui.elf