JDCloud RE-CP-03: set to build BL2 + FIP and fix ENV OFFSET

[lgs2007m]

The stock BL2 and FIP of JDCloud RE-CP-03 were builted WITH secure boot, we should build and replace them together. Only replacing FIP will cause bricks.

But The stock BL2 and FIP of CMCC RAX3000M eMMC were builded WITHOUT secure boot, we only need to build and replace FIP.

The single boot gpt of JDCloud RE-CP-03 and CMCC RAX3000M eMMC is like that:

Device	Start	End	Sectors	Size	Name
/dev/mmcblk0p1	8192	9215	1024	512K	u-boot-env
/dev/mmcblk0p2	9216	13311	4096	2M	factory
/dev/mmcblk0p3	13312	17407	4096	2M	FIP
/dev/mmcblk0p4	17408	50175	32768	16M	kernel
/dev/mmcblk0p5	50176	1098751	1048576	512M	rootfs

We can see the u-boot-env offset is 8192 sectors * 512 bytes per sector = 4194304 bytes = 0x400000 bytes.