ARM: OMAP3: Disable broken omap3_set_off_timings function

ARM: OMAP3: Disable broken omap3_set_off_timings function

Commit c589eb3869a8 (ARM: OMAP3: VC: calculate ramp times)
started using regulator slew rates for calculating the idle
mode start-up times. This works fine for I2C4 controlled
regulator scaling as the regulators are never completely
turned off.

For sys_off_mode pin controlled PMIC scripts, the slew rate
based calculations won't work at all as the regulators are
completely turned off and the start-up time is much longer.

This means currently omap3_set_off_timings currently has
zero chance of working on any real hardare. The current code
is broken in at least the following ways:

1. It attempts to use the default ULONG_MAX value for the
   oscillator start-up value as we're currently never
   initializing the start-up value.

2. It relies on a magic number potentially set by the
   bootloader for volsetup2 register.

3. If no magic value is passed, it attempts to calculate
   voltsetup2 register based on the regulator slew rate.
   This won't work as there is roughly at least five
   times the delay needed for turning on vdd1 and vdd2
   regulators.

4. It does duplicate register write to OMAP3_PRM_VOLTOFFSET

5. It duplicates the code for omap_usec_to_32k unnecessarily

6. It initialized global registers twice, once for each channel

Let's just remove the broken code and call omap3_set_i2c_timings
directly, we're better off with this function doing nothing until
it's fixed. And otherwise further fixes to omap3_set_off_timings
will be unreadable.

And let's get rid of omap3_set_clksetup as that's not needed
for off-idle controlled by I2C4 as in that case the oscillator
is never shut down.

Cc: Kevin Hilman <khilman@linaro.org>
Cc: Nishanth Menon <nm@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>