meta-inspur: update Yocto compat for gatesgarth

Since the current release of Yocto is gatesgarth, Add and support for
gatesgarth(current) and dunsfell(previous) in meta-inspur layer.

Also, remove the two earlier releases(warrior and zeus).

Tested: Built successfully on fp5280g2 and on5263m5.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: Id8d2b3dfcbe9fff807782f20bab013a3a8ddec41
3 files changed