ARM: bcm2835: add I2C controllers to DT

The BCM2835 has 3 identical I2C controllers. Instantiate them all in the
SoC .dtsi file, and enable the relevant two in the Raspberry Pi board
.dts file.

Note that on the Raspberry Pi Model B revision 1, I2C0 is connected to
the general-purpose expansion header, and I2C1 is connected to the camera
connector. Revision 2 of the board swaps these assignments:-(

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
ARM: bcm2835: defconfig updates

Now that we have an SDHCI driver, enable the block layer, and common
filesystems; MSDOS/VFAT for the SoC-required firmware partition, ext2/3/4
for a root partition.

Add tmpfs, NFS, file locking, file notify, networking, and NLS to support
distro expectations.

Enable GPIO_SYSFS to allow GPIO twiddling from user-space; likely a
common activity on this hardware.

Enable I2C.

Remove bogus CONFIG_DEFAULT_MMAP_MIN_ADDR so that applications running as
non-root actually work; without this, execve() immediately triggers
SIGKILL. This setting was sourced from some downstream defconfig early
during upstream Raspberry Pi support development.

Other non-semantic diffs due to rebuilding defconfig using the latest
Kconfig defaults etc.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>