get_group_pins() "returns" a pointer to an array of const objects, through
a pointer parameter. Fix the prototype so what's pointed at by the returned
pointer is const, rather than the function parameter being const.

This also allows the removal of a cast in each of the two current pinmux
drivers.
Signed-off-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

This adds a driver for the U300 pinmux portions of the system
controller "SYSCON". It also serves as an example of how to use
the pinmux subsystem. This driver also houses the platform data
for the only supported platform.

This deletes the old U300 driver in arch/arm/mach-u300 and
replace it with a driver using the new subsystem.

The new driver is considerably fatter than the old one, but it
also registers all 467 pins of the system and adds the power
and EMIF pin groups and corresponding functions. The idea
is to use this driver as a a reference for other
implementation so it needs to be as complete and verbose
as possible.
Reviewed-by: NBarry Song <21cnbao@gmail.com>
[Fixup for changed function names and semantics in the v10 patch]
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>