mem_cgroup_move_task() is now called from ->post_attach
instead of ->attach thanks to LTS commit 52526076a5
("memcg: relocate charge moving from ->attach to ->post_attach").
Hence remove ->attach callback which sneaked back into
lsk-v4.4-android tree in the LSK merge commit 334ca3ed18
("Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android").
Otherwise we run into following build warning reported on KernelCI
https://kernelci.org/build/lsk/branch/linux-linaro-lsk-v4.4-android/kernel/lsk-v4.4-17.11-android-844-g6a7d9fbcf946/
mm/memcontrol.c:5337:12: warning: initialization from incompatible pointer type [-Wincompatible-pointer-types]
Fixes: LSK commit 334ca3ed18
("Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android")
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>