package/luajit: add BR2_aarch64_be support

ARM64 big-endian is supported since
https://github.com/LuaJIT/LuaJIT/commit/3143b218946395834f0bfef741061ac6ef3f5b56



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>