mfd: Include all drivers in subsystem menu

It is currently not possible to select the SA1100 or Vexpress
drivers in the MFD subsystem, because the menu for the entire
subsystem ends before these options are presented.

Move the main menu closing and the endif for HAS_IOMEM to the
end of the file so these are selectable again.

Cc: stable@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>