Documentation/ABI: Mark /sys/kernel/fadump_* sysfs files deprecated

Add a deprecation note in FADump sysfs ABI documentation files and
move them from ABI/testing to ABI/obsolete directory.

Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
[mpe: Use a proper table to fix errors from the documentation build]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191211160910.21656-6-sourabhjain@linux.ibm.com