MFC r257207, r261161, r261163:

  Update the hard-float version of the fenv functions to use the VFP unit.
  Any other floating-point unit is unsupported on ARM.

  Use __fenv_static for all static inline functions.

  Correctly shift the mask when masking/unmasking exceptions.
MFC r265012, r265191, r265289, r265310

r265012:
Fix the gpio-specifier decoding by respecting the GPIO controller's
#gpio-cells property.

Add a new ofw_bus method (OFW_BUS_MAP_GPIOS()) that allows the GPIO
controller to implement its own mapping to deal with gpio-specifiers,
allowing the decoding of gpio-specifiers to be controller specific.

The default ofw_bus_map_gpios() decodes the linux standard (#gpio-cells =
<2>) and the FreeBSD standard (#gpio-cells = <3>).

It pass the gpio-specifier flag field to the children as an ivar variable so
they can act upon.

r265191:
Remove unnecessary headers.  Sort out the headers.  Add a missing header on
ofw_gpiobus.c (it was working because of sys/libkern.h).

r265289:
eally sort out the headers.

sys/systm.h must always come after sys/param.h.

Remove sys/types.h which should never be included together with sys/param.h.

Add sys/malloc.h for correctness even if it seems to don't be needed.

Remove more unused headers found by unusedinc (from bde@).

r265310:
Move gpiobus routines to dev/gpio.  Avoid polluting ofw_bus with bus
specific parts.