mem: improve autodetection of hugepage counts on 32-bit

mem: improve autodetection of hugepage counts on 32-bit

For non-legacy mode, we are preallocating space for hugepages, so
we know in advance which pages we will be able to allocate, and
which we won't. However, the init procedure was using hugepage
counts gathered from sysfs and paid no attention to hugepage
sizes that were actually available for reservation, and failed
on attempts to reserve unavailable pages.

Fix this by limiting total page counts by number of pages
actually preallocated.

Also, VA preallocate procedure only looks at mountpoints that are
available, and expects pages to exist if a mountpoint exists. That
might not necessarily be the case, so also check if there are
hugepages available for a particular page size on a particular
NUMA node.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Tested-by: Jananee Parthasarathy <jananeex.m.parthasarathy@intel.com>