[ARM] 4806/1: ixp4xx: Ethernet support for the nslu2 and nas100d boards

Enables the new ixp4xx qmgr and npe drivers in ixp4xx_defconfig.

Sets up the corresponding platform data for the nslu2 and nas100d
boards, and reads the ethernet MAC address from the internal flash.

Tested on both little-endian and big-endian kernels.

Tested-by: Tom King <tom@websb.net>

Signed-off-by: Rod Whitby <rod@whitby.id.au>
Signed-off-by: Michael Westerhof <mwester@dls.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>