mmc: core: Fix blk_status_t handling

mmc: core: Fix blk_status_t handling

Sparse spits out this following warning:

drivers/mmc/core/queue.c:311:21: warning: incorrect type in assignment (different base types)
drivers/mmc/core/queue.c:311:21:    expected int ret
drivers/mmc/core/queue.c:311:21:    got restricted blk_status_t [usertype]
drivers/mmc/core/queue.c:314:21: warning: incorrect type in assignment (different base types)
drivers/mmc/core/queue.c:314:21:    expected int ret
drivers/mmc/core/queue.c:314:21:    got restricted blk_status_t [usertype]
drivers/mmc/core/queue.c:336:16: warning: incorrect type in return expression (different base types)
drivers/mmc/core/queue.c:336:16:    expected restricted blk_status_t
drivers/mmc/core/queue.c:336:16:    got int [assigned] ret

ret is only used for blk_status_t types, so make it that type.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211215011336.194089-1-joel@jms.id.au
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>