Revert "Abolish get_available_num_host_mem_channels"

[joelsmithTT]

Reverts commit 3210bd9 from #393.

Issue

Metal CI failure tracked in tenstorrent/tt-metal#15675

Description

The reverted commit removed logic that allowed applications to request more hugepages than available to UMD. Previously, UMD would issue a warning in such cases. However, this created a potential safety issue since applications had no visibility into partial hugepage allocation (e.g., requesting 4 pages but receiving only 2).

This situation could lead to:

• Host software segfaults when accessing unmapped pages
• More critically, device software could potentially corrupt host physical address space by writing to nonexistent pages

While the original change (making excessive hugepage requests a fatal error) improved safety, particularly in conjunction with IOMMU enablement, it caused failures in Metal CI tests that (possibly unintentionally?) request more hugepages than available. This revert is a temporary measure until the Metal CI tests can be updated.

List of the changes

• Revert 3210bd9
• Update comment documentation

Testing

CI

API Changes

There are no API changes in this PR.