Include <linux/i2c.h> in all ep93xx platforms.

Patch "5311/1: add core support for built in i2c bus" will cause build errors due to the following in
arch/arm/mach-ep93xx/include/mach/platform.h:

+void ep93xx_register_i2c(struct i2c_board_info *devices, int num);

The i2c.h header needs to be included in order to define struct i2c_board_info.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>