mmc: cast unsigned int to typeof(sector_t) to avoid unexpected error

card->csd.capacity is defined as "unsigned int", and sector_t is defined as
"u64" or "unsigned long" (depends on CONFIG_LBDAF). Thus, sector_t data
might have strange data (see below). This patch cast it to typeof(sector_t)
Special thanks to coverity <http://www.coverity.com

>

ex) if sector_t was u64

        unsigned int data;
        sector_t sector;

        data = 0x800000;
        sector = (data << 8); // 0xffffffff80000000
        sector = (((typeof(sector_t))data) << 8); // 0x80000000

or

        data = 0x80000000;
        sector = (data << 8); // 0x0
        sector = (((typeof(sector_t))data) << 8); // 0x8000000000

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>