i2c-designware: use div_u64 to fix link

This fixes the following link error:

  drivers/built-in.o: In function `dw_i2c_probe':
  of_iommu.c:(.text+0x18c8f0): undefined reference to `__aeabi_uldivmod'
  make: *** [vmlinux] Error 1

Signed-off-by: Vincent Stehlé <vincent.stehle@freescale.com>
Tested-by: Kevin Hilman <khilman@linaro.org>
Reviewed-by: Christian Ruppert <christian.ruppert@abilis.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>