i2c: mxs: Silence a clang warning

Change the of_device_get_match_data() cast to (uintptr_t)
to silence the following clang warning:

drivers/i2c/busses/i2c-mxs.c:802:18: warning: cast to smaller integer type 'enum mxs_i2c_devtype' from 'const void *' [-Wvoid-pointer-to-enum-cast]

Reported-by: kernel test robot <lkp@intel.com>
Fixes: c32abd8b

 ("i2c: mxs: Remove unneeded platform_device_id")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>