Current calculation of shared cache size is from the node (die) scope,
but we hope 'lscpu' to show the shared cache size of the whole package
for multi-die chips (e.g., Loongson-3C5000L, which contains 4 dies in
one package). So fix it by multiplying nodes_per_package.
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>