octeontx2-af: fix out-of-bounds read setting MSI-X irq affinity

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

octeontx2-af: fix out-of-bounds read setting MSI-X irq affinity

rvu_register_interrupts() walks every MSI-X vector and uses strstr()
to match "Mbox" or "FLR" in irq_name before pinning those interrupts
to CPU 0. irq_name is a per-vector NAME_SIZE buffer, but not every
slot is populated before this loop runs. strstr() keeps scanning until
it finds a NUL terminator, so an uninitialized slot can trigger a KASAN
slab-out-of-bounds read at boot when debug options are enabled.

Use strnstr() with NAME_SIZE to bound the search within each vector's
name buffer.