i2c-omap: Add high-speed support to omap-i2c

Omap2430 has additional support for high-speed I2C.

This patch moves I2C speed parameter (from module) to platform data.
Also added basic High Speed support based on I2C bus speed.

This patch is tested for high speed I2C (with TWL4030 Keypad) and works as
expected.

Also change the 2430 i2chs_fck names to use the standard naming.

Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Syed Mohammed Khasim <x0khasim@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>