mm: convert memory block states (MEM_*) macros to enum

mm: convert memory block states (MEM_*) macros to enum

Patch series "mm: Convert memory block states (MEM_*) macros to enums", v2.

The MEM_* constants indicating the state of a memory block are currently
defined as macros, meaning their definitions will be omitted from the
debuginfo on most kernel builds.  This makes it harder for debuggers to
correctly map the block state at runtime, which can be quite useful when
analysing errors related to memory hot plugging and unplugging with tools
such as drgn.

Converting the constants to an enum ensures the correct information is
emitted by the compiler and available for the debugger, without needing to
hard-code them into the debugger and track their changes.

This patch series aims to replace the current macros with a newly created
enum named memory_block_state, while also taking advantage of the compile
time guarantees that we get when using enums.

The first patch does the conversion of the macros to an enum, while the
2nd and 3rd patches use this enum to clean up some type declarations and
make sure that only valid values are used.

This patch (of 3):

Converting the MEM_* constants from macros to an enum ensures that their
values will be correctly emitted in the debug symbols, making it easier to
trace the meaning of each value when debugging with tools such as drgn,
without the need to hard-code the values.

Since the values are mutually exclusive and they are not exposed directly
to userspace, I also dropped the misleading pattern (1<<X) that made it
look like they were combinable flags.

Link: https://lkml.kernel.org/r/20251029195617.2210700-1-linux@israelbatista.dev.br
Link: https://lkml.kernel.org/r/20251029195617.2210700-2-linux@israelbatista.dev.br
Signed-off-by: Israel Batista <linux@israelbatista.dev.br>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Omar Sandoval <osandov@osandov.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>