OMAP: mux: Add support for control module split in several partitions

OMAP: mux: Add support for control module split in several partitions

Starting on OMAP4, the pin mux configuration is located in two
different partitions of the control module (CODE_PAD and WKUP_PAD).
The first one is inside the core power domain whereas the second
one is inside the wakeup.
- Add the capability to add any number of partition during board init
time depending of Soc partitioning.
- Add some init flags as well in order to avoid explicit Soc version
check inside the mux core code.
- Add a comment with mux0 mode on top of omap_mux/board/<partition>
if the current mux mode is not the default one.

Thanks to Tony Lindgren <tony@atomide.com> for the following improvements:
- Add omap_mux_get for getting the partition data so platform level
device code can use it.
- Fix the rx51 board code to use the new API.
- Do not store the partition for each mux entry. Look up the partition
for debugfs instead.

Thanks to Dan Murphy <dmurphy@ti.com> for testing on OMAP4 and reporting
a couple of bugs.
Thanks to Anand Gadiyar <gadiyar@ti.com> for testing on OMAP3 zoom and
bug report.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Tested-by: Murphy Dan <dmurphy@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Anand Gadiyar <gadiyar@ti.com>