i2c-nomadik: move header to <linux/platform_data/i2c-nomadik.h>

The header and driver are only used by arm/mach-u8500 (and potentially
arm/mach-nomadik), but the STA2X11 I/O Hub exports on PCIe a number of
devices, including i2c-nomadik.  This patch allows compilation of the
driver under x86.

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>
Acked-by: Giancarlo Asnaghi <giancarlo.asnaghi@st.com>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>