selftests/mm: change NR_CHUNKS_HIGH for aarch64

selftests/mm: change NR_CHUNKS_HIGH for aarch64

Although there is a provision for 52 bit VA on arm64 platform, it remains
unutilised and higher addresses are not allocated.  In order to
accommodate 4PB [2^52] virtual address space where supported,
NR_CHUNKS_HIGH is changed accordingly.

Array holding addresses is changed from static allocation to dynamic
allocation to accommodate its voluminous nature which otherwise might
overflow the stack.

Link: https://lkml.kernel.org/r/20230323060121.1175830-3-chaitanyas.prakash@arm.com
Signed-off-by: Chaitanya S Prakash <chaitanyas.prakash@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>