arm: Implement copy_thread_tls

arm: Implement copy_thread_tls

BugLink: https://bugs.launchpad.net/bugs/1862227
commit 167ee0b82429cb5df272808c7a21370b7c961ab2 upstream.

This is required for clone3 which passes the TLS value through a
struct rather than a register.

Signed-off-by: Amanieu d'Antras <amanieu@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: <stable@vger.kernel.org> # 5.3.x
Link: https://lore.kernel.org/r/20200102172413.654385-4-amanieu@gmail.com
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>