leaking_addresses: add support for 5 page table levels

Currently script only supports 4 page table levels because of the way
the kernel address regular expression is crafted. We can do better than
this. Using previously added support for kernel configuration options we
can get the number of page table levels defined by
CONFIG_PGTABLE_LEVELS. Using this value a correct regular expression can
be crafted. This only supports 5 page tables on x86_64.

Add support for 5 page table levels on x86_64.

Signed-off-by: Tobin C. Harding <me@tobin.cc>