powerpc/pseries: rename numa_dist_table to form2_distances

The name of the local variable holding the "form2" property address
conflicts with the numa_distance_table global.

This patch does 's/numa_dist_table/form2_distances/g' over the function,
which also renames numa_dist_table_length to form2_distances_length.

Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211109064900.2041386-1-npiggin@gmail.com