ARM: ux500: simplify secondary CPU boot

This removes a lot of ancient cruft from the Ux500 SMP boot.
Instead of the pen grab/release, just point the ROM to
secondary_boot() and start the second CPU there, then send
the IPI.

Use our own SMP enable method. This enables us to remove the
last static mapping and get both CPUs booting properly.

Tested this and it just works.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>