pci: reduce minimum chunking granularity in physmem allocator to 1 (i.e. 2 caps at each level)
pci: reduce minimum chunking granularity in physmem allocator to 1 (i.e. 2 caps at each level)

This wastes memory, but is needed to ensure that we can always
allocate caps to BARs at the correct granularity. I needed it to get
the framebuffer cap working on an Nvidia card; hopefully it doesn't
break other hardware :(

modeswitch/barrelfish,modeswitch/barrelfish,modeswitch/barrelfish,modeswitch/barrelfish,modeswitch/barrelfish