Allow to switch off check of PCI expansion ROMs

[rainer]

Some kernels seem to have problems reading the ROM (reported by S. Clormann, using kernel 2.6.28.5). This results in errors like:

CRIT   :  [2009-02-27T10:21:47+0100] msg=<Not accessible or not a regular file 
   (Read error / Input/output error)>, path=</sys/bus/pci/devices/0000:00:06.0/rom>

which are accompanied by:

kernel: vmap allocation failed: use vmalloc=<size> to increase size.

We should have an option to switch off the check.

[rainer]

Fixed in changeset [223].