cgroup/dmem: Select PAGE_COUNTER

cgroup/dmem: Select PAGE_COUNTER

The dmem cgroup the page counting API implemented behing the
PAGE_COUNTER kconfig option. However, it doesn't select it, resulting in
potential build breakages. Select PAGE_COUNTER.

Fixes: b168ed458dde ("kernel/cgroup: Add "dmem" memory accounting cgroup")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501111330.3VuUx8vf-lkp@intel.com/
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Simona Vetter <simona.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20250113092608.1349287-1-mripard@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>