Bug#1059960: flash-kernel: Please add loong64 binary output for Loongarch

[zhangdandan]

Hi maintainer,

debian/control: enable building for loong64.
Please take care of the patch I added for loong64 in 
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1059960#10.

Could you add loong64 support in the next upload?

Thanks
Dandan Zhang