util/selfmap: Use dev_t and ino_t in MapInfo

util/selfmap: Use dev_t and ino_t in MapInfo

Use dev_t instead of a string, and ino_t instead of uint64_t.
The latter is likely to be identical on modern systems but is
more type-correct for usage.

Tested-by: Helge Deller <deller@gmx.de>
Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>