netxen: fix the version code macro

Correct firmware encoding is 8 bit major, 8 bit minor and
16 bit subversion. Flash has sizes rightly set, but original
driver submission messed it leaving 16 bit major and 8 bit
subversion.

Also fix a infinite loop when cut-thru file firmware is
invalid.

Signed-off-by: Dhananjay Phadke <dhananjay@netxen.com>
Signed-off-by: David S. Miller <davem@davemloft.net>