[SCSI] esp_scsi: Use DIV_ROUND_UP

Use the macro DIV_ROUND_UP and eliminate the variable rounded_up, as
suggested by Matthew Wilcox.

Signed-off-by: Julia Lawall <julia@diku.dk>
Cc: David Miller <davem@davemloft.net>
Reviewed-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>