mm/damon/Kconfig: Remove unnecessary PAGE_EXTENSION setup

mm/damon/Kconfig: Remove unnecessary PAGE_EXTENSION setup

Commit 13d49dbd0123 ("mm/damon: implement primitives for the virtual
memory address spaces") of linux-mm[1] makes DAMON_VADDR to set
PAGE_IDLE_FLAG.  PAGE_IDLE_FLAG sets PAGE_EXTENSION if !64BIT.  However,
DAMON_VADDR do the same work again.  This commit removes the unnecessary
duplicate.

[1] https://github.com/hnaz/linux-mm/commit/13d49dbd0123

Link: https://lkml.kernel.org/r/20210806095153.6444-2-sj38.park@gmail.com
Fixes: 13d49dbd0123 ("mm/damon: implement primitives for the virtual memory address spaces")
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>