tools: libxl: Use correct printf format for uint64_t

tools: libxl: Use correct printf format for uint64_t

Since 25652f232cbe "tools/libxl: detect and avoid conflicts with RDM"
the build is broken for x86_32 and arm32 with:

libxl_dm.c: In function ‘libxl__domain_device_construct_rdm’:
libxl_dm.c:349:13: error: format ‘%lx’ expects argument of type ‘long unsigned int’, but argument 8 has type ‘uint64_t’ [-Werror=format=]
             LOG(ERROR, "RDM conflict at 0x%lx.\n", d_config->rdms[i].start);
             ^
libxl_dm.c:352:13: error: format ‘%lx’ expects argument of type ‘long unsigned int’, but argument 8 has type ‘uint64_t’ [-Werror=format=]
             LOG(WARN, "Ignoring RDM conflict at 0x%lx.\n",

Use PRIx64 for these.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Cc: Tiejun Chen <tiejun.chen@intel.com>