Use explicit type to placate the compiler.

 | proc_parse.c: In function 'vma_get_mapfile':
 | proc_parse.c:282:6: error: format '%lx' expects argument of type 'long unsigned
 | int', but argument 5 has type 'uint64_t' [-Werror=format=]
 |       pr_err("Strange file mapped at %lx [%s]:%d.%d.%ld\n",
 |       ^
 | proc_parse.c:335:5: error: format '%lx' expects argument of type 'long unsigned
 | int', but argument 5 has type 'uint64_t' [-Werror=format=]
 |      pr_err("Failed to resolve mapping %lx filename\n",
 |      ^
 | cc1: all warnings being treated as errors

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>