mmc: mxcmmc: Silence a clang warning

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

drivers/mmc/host/mxcmmc.c:1028:18: warning: cast to smaller integer type 'enum mxcmci_type' from 'const void *' [-Wvoid-pointer-to-enum-cast]

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 8223e885

 ("mmc: mxc: Convert the driver to DT-only")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20220526010022.1163483-1-festevam@gmail.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>