omap: mux: Add new style pin multiplexing code for omap3

Initially only for 34xx. This code allows us to:

- Make the code more generic as the omap internal signal
  names can stay the same across omap generations for some
  devices

- Map mux registers to GPIO registers that is needed for
  dynamic muxing of pins during off-idle

- Override bootloader mux values via kernel cmdline using
  omap_mux=some.signa1=0x1234,some.signal2=0x1234

- View and set the mux registers via debugfs if
  CONFIG_DEBUG_FS is enabled

Cc: Mike Rapoport <mike@compulab.co.il>
Cc: Benoit Cousson <b-cousson@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Documentation/kernel-parameters.txt

@@ -1787,6 +1787,11 @@ and is between 256 and 4096 characters. It is defined in the file
 			waiting for the ACK, so if this is set too high
 			interrupts *may* be lost!
 
+	omap_mux=	[OMAP] Override bootloader pin multiplexing.
+			Format: <mux_mode0.mode_name=value>...
+			For example, to override I2C bus2:
+			omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
+
 	opl3=		[HW,OSS]
 			Format: <io>