[ARM] pxa: add default config for littleton

default to

- PXA300/PXA310 support only (there isn't any littleton board with PXA320
  processor for now)

- smc91x ethernet support with NFS rootfs

- LCD framebuffer support with graphics console

Signed-off-by: eric miao <eric.miao>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>