backports: add support for voltage / current regulator drivers

backports: add support for voltage / current regulator drivers

This backports the latest regulator drivers for kernels >= 3.4.
We enable the regulator only on kernels >= 3.4 given that
it relies on the new probe deferral mechanism which would
otherwise mean having to support drivers that do not probe
correctly. Note that 3.2 had a base regulator implementation
but that was just stubs.

I did look into a way to upgrade the core kernel regulator
but given that it relies on late_initcall() and core_initcall()
we can't update this part of the kernel. I even looked at
using ksplice for this but it seems ksplice can't be used to
update init sections on the vmlinux ELF. I also haven't much
updates to these routines since 3.4 except for 86f5fcfc.

1   2.6.24              [  OK  ]
2   2.6.25              [  OK  ]
3   2.6.26              [  OK  ]
4   2.6.27              [  OK  ]
5   2.6.28              [  OK  ]
6   2.6.29              [  OK  ]
7   2.6.30              [  OK  ]
8   2.6.31              [  OK  ]
9   2.6.32              [  OK  ]
10  2.6.33              [  OK  ]
11  2.6.34              [  OK  ]
12  2.6.35              [  OK  ]
13  2.6.36              [  OK  ]
14  2.6.37              [  OK  ]
15  2.6.38              [  OK  ]
16  2.6.39              [  OK  ]
17  3.0.65              [  OK  ]
18  3.1.10              [  OK  ]
19  3.2.38              [  OK  ]
20  3.3.8               [  OK  ]
21  3.4.32              [  OK  ]
22  3.5.7               [  OK  ]
23  3.6.11              [  OK  ]
24  3.7.9               [  OK  ]
25  3.8.0               [  OK  ]
26  3.9-rc1             [  OK  ]

real    39m35.615s
user    1068m47.428s
sys     155m55.657s

Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>