staging: greybus: sdio: Prefer u32 over uint32_t

It fixes the following issue reported by checkpatch.pl:
Prefer kernel type 'u32' over 'uint32_t'

Signed-off-by: Franck Demathieu <fdemathieu@gmail.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>