LOCAL HACK: ARM: bcm2835: enable enc28j60 SPI device

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
HACK: create a Tegra+BCM2835 defconfig

This requires neutering some of the Tegra assembly files, since they use
opcodes that ARMv6 doesn't support. However, the resultant kernel does
boot on the Pi!