parisc: enable DEVTMPFS, DEVTMPFS_MOUNT and BLK_DEV_INITRD in defconfigs

Latest udev requires that DEVTMPFS and DEVTMPFS_MOUNT are enabled, else
initrd will fail to find root filesystem. Enable missing BLK_DEV_INITRD
for B180 and C3000 machines.

Signed-off-by: Helge Deller <deller@gmx.de>