man/man2/{mbind,set_mempolicy}.2: Document MPOL_PREFERRED_MANY

man/man2/{mbind,set_mempolicy}.2: Document MPOL_PREFERRED_MANY

Browsing a header file in the kernel source and saw the memory policy
enum used for mbind() and set_mempolicy() using an entry that I didn't
recognize.  I man 2'd both system calls and didn't see an entry for
MPOL_PREFERRED_MANY.  The commit on the enum entry:

linux.git b27abaccf8e8 (2021-09-02; "mm/mempolicy: add
MPOL_PREFERRED_MANY for multiple preferred nodes")

The commit message gives the rationale as to why the MPOL_PREFERRED_MANY
mode would be beneficial.  Giving the ability to set the memory policy
to target different tiers of memory over various NUMA nodes.

Cc: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Matthew Cassell <mcassell411@gmail.com>
Message-ID: <20250220225232.2138-1-mcassell411@gmail.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>