dmaengine: nbpfaxi: Fix memory corruption in probe()

In the Linux kernel, the following vulnerability has been resolved:

dmaengine: nbpfaxi: Fix memory corruption in probe()

The nbpf->chan[] array is allocated earlier in the nbpf_probe() function

and it has "num_channels" elements. These three loops iterate one

element farther than they should and corrupt memory.

The changes to the second loop are more involved. In this case, we're

copying data from the irqbuf[] array into the nbpf->chan[] array. If

the data in irqbuf[i] is the error IRQ then we skip it, so the iterators

are not in sync. I added a check to ensure that we don't go beyond the

end of the irqbuf[] array. I'm pretty sure this can't happen, but it

seemed harmless to add a check.

On the other hand, after the loop has ended there is a check to ensure

that the "chan" iterator is where we expect it to be. In the original

code we went one element beyond the end of the array so the iterator

wasn't in the correct place and it would always return -EINVAL. However,

now it will always be in the correct place. I deleted the check since

we know the result.