debian/control: add loong64 support

Dear Maintainers,

I have added support for the "loong64" architecture in the debian/control file of the pktanon software package. The updated Architecture field now includes "loong64" along with other architectures:

Architecture: amd64 arm64 i386 loong64 mips64el mipsel ppc64el alpha hppa ia64 m68k powerpc ppc64 riscv64 sh4 sparc64 x32

Thank you for your attention to this update.