Adding condition to warn about 0 divider value.
It was observed while accessing svec-flash, if frequency for flash is not defined correctly i.e
in operation range of chip and host(i.e vme or pci), divider value 0 doesn't allow flash transfers.

Signed-off-by Mamta Shukla <mamta.ramendra.shukla@cern.ch>
Suggested-by: Federico Vaga <federico.vaga@cern.ch>