Before the board level GPIO handling is converted from GPIO numbers to
GPIO descriptors, split late_init() into functional blocks and move
them to separate functions.

While being at it, drop machine type check from late_init() - the
function is now called from the board init_late callback so there is
no need for yet another applicability check.
Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>