nfit_test: fix buffer overrun, add sanity check

It turns out that we were overrunning the 'nfit_buf' buffer in
nfit_test0_setup() in the (t->setup_hotplug == 1) case because we failed to
correctly account for all of the acpi_nfit_memory_map structures.

Fix the structure count which will increase the allocation size of
'nfit_buf' in nfit_test0_alloc().  Also add some WARN_ON()s to
nfit_test0_setup() and nfit_test1_setup() to catch future issues where the
size of the buffer doesn't match the amount of data we're writing.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>