omap3: zoom: Drop i2c-1 speed to 2400

The I2C-1 bus frequency on zoom2/zoom3/sdp3630 should be 2.4 MHz.
The speed is limited by TWL5030/GAIA; a higher speed could lead to errors
on the interface.

The maximum I2C speed depends on the system clock for GAIA:
2.2 MHz (sys-clk = 19.2 MHz)
2.4 MHz (sys-clk = 26 MHz)
2.9 MHz (sys-clk = 38.4 MHz)

For Zoom2/Zoom3/SDP3630 the system clock is 26Mhz
and hence choose 2.4Mhz for I2C1 bus speed

Signed-off-by: Vikram Pandita <vikram.pandita@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>