tools/libxl: return socket id from libxl_psr_cat_get_l3_info

tools/libxl: return socket id from libxl_psr_cat_get_l3_info

The entries returned from libxl_psr_cat_get_l3_info are assumed
to be socket-continuous. But this is not true in the hotplug case.

This patch gets the socket bitmap for all the sockets on the system
first and stores the socket id in the structure libxl_psr_cat_info in
libxl_psr_cat_get_l3_info. The xl or similar consumers then can display
socket information correctly.

Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>