staging: vt6655: Use incrementation in `idx`

Increment `idx` in a loop instead of adding the loop counter
`i` to do so. Delete increments of `i` that were rendered
unnecessary by this change.

Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Karolina Drobnik <karolinadrobnik@gmail.com>
Link: https://lore.kernel.org/r/9affeaf40ddb31e03b21db9acd099db4d80da179.1636729147.git.karolinadrobnik@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>