scsi: initio: Remove redundant variable 'rb'

The variable 'rb' is being assigned a value but it isn't being read
afterwards. The assignment is redundant and so 'rb' can be removed.

Cleans up clang scan build warning:

warning: Although the value stored to 'rb' is used in the enclosing
expression, the value is never actually read from 'rb'[deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20240116112606.2263738-1-colin.i.king@gmail.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>