cxgb3: fix up vpd strings for kstrto*()

The vpd strings are left justified, in a fixed length array, with possible
trailing white space and no NUL.  So fix them up before calling kstrto*().

This is a recent regression which causes cxgb3 to fail to load.

Fixes: e72c932d ("cxgb3: Convert simple_strtoul to kstrtox")

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: David S. Miller <davem@davemloft.net>