regulator: mc13892: sanity check num_regulators parsed vs. registered

regulator: mc13892: sanity check num_regulators parsed vs. registered

Imagine a situation where a device tree has a few regulators in an
appropriate node:

regulators {
	sw1 {
		..
	};

	vvideo {
		..
	};

	:

	vfake {
		..
	};

	vtypo {
		..
	};
};

In the above example, the node name "vfake" is an attempt to match a
regulator name inside the driver which just so happens to not exist. The
node name "vtypo" represents an accidental typographical error in a
regulator name which may have been introduced to a device tree.

In these cases, the number of regulators the mc13892 driver thinks it has
does not match the number of regulators it parsed and registered. Since
it will go over this array based on this number, it will actually
re-register regulator "0" (which happens to be SW1) over and over
again until it reaches the number, resulting in messages on the kernel
log such as these:

SW1: at 1100 mV
VVIDEO: at 2775mV
:
SW1: at 1100 mV
SW1: at 1100 mV

.. up to that number of "mismatched" regulators. Nobody using DT can/will
consume these regulators, so it should not be possible for it to cause any
real regulator problems or driver breakages, but it is an easy thing to
miss in a kernel log and is an immediate indication of a problem with the
device tree authoring.

This patch effectively sanity checks the number of counted children of
the regulators node vs. the number that actually matched driver names,
and sets the appropriate num_regulators value. It also gives a little
warning for device tree authors that they MAY have screwed something up,
such that this patch does not hide the device tree authoring problem.

Signed-off-by: Matt Sealey <matt@genesi-usa.com>
Tested-by: Steev Klimaszewski <steev@genesi-usa.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>