x86/mm: Reduce header dependencies in <asm/set_memory.h>

Commit:

  03b122da ("x86/sgx: Hook arch_memory_failure() into mainline code")

... added <linux/mm.h> to <asm/set_memory.h> to provide some helpers.

However the following commit:

  b3fdf939 ("x86/mce: relocate set{clear}_mce_nospec() functions")

... moved the inline definitions someplace else, and now <asm/set_memory.h>
just declares a bunch of mostly self-contained functions.

No need for the whole <linux/mm.h> inclusion to declare functions; just
remove that include. This helps avoid circular dependency headaches
(e.g. if <linux/mm.h> ends up including <linux/set_memory.h>).

This change requires a couple of include fixups not to break the
build:

* <asm/smp.h>: including <asm/thread_info.h> directly relies on
  <linux/thread_info.h> having already been included, because the
  former needs the BAD_STACK/NOT_STACK constants defined in the
  latter. This is no longer the case when <asm/smp.h> is included from
  some driver file - just include <linux/thread_info.h> to stay out
  of trouble.

* sev-guest.c relies on <asm/set_memory.h> including <linux/mm.h>,
  so we just need to make that include explicit.

[ mingo: Cleaned up the changelog ]

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20241212080904.2089632-3-kevin.brodsky@arm.com