tools: implement the new libxl get hw info interface

tools: implement the new libxl get hw info interface

This patch implements the new libxl get hw info interface,
'libxl_psr_get_hw_info', which is suitable to all psr allocation
features. It also implements corresponding list free function,
'libxl_psr_hw_info_list_free' and makes 'libxl_psr_cat_get_info' call
'libxl_psr_get_hw_info' to avoid redundant code in libxl_psr.c.

Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>