Staging: mt29f_spinand: Remove space after a cast

Modify retval to reflect removal of space during cast operation.
Checkpatch found this issue.

CHECK: No space is necessary after a cast

Signed-off-by: Eva Rachel Retuya <eraretuya@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>