tools: Remove dependency of jailhouse tool on cell-config.h

tools: Remove dependency of jailhouse tool on cell-config.h

Two things caused jailhouse.h and, thus, tools/jailhouse.c to depend on
the cell configuration header: the definition of the JAILHOUSE_ENABLE
IOCTL and the maximum cell name length in config files.

The first dependency is not only unneeded (the command line tool passed
the an uninterpreted blob via JAILHOUSE_ENABLE), it also made the driver
ABI change each time we updated the config format. So replace the
reference to struct jailhouse_system in JAILHOUSE_ENABLE with a symbolic
"void *".

The second dependency is also unneeded: While the name length used in
configs and, thus, also inside the driver to reference cells should be
identical to the lengths we use in struct jailhouse_cell_id, there is no
hard dependency. In the worst case (different lengths), we would fail to
address cells by name. However, these lengths are unlikely to change. So
simply define our own name length for that struct and test for
deviations during the driver build.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>