README: Point to the official Yocto git tree

Point to the official Yocto git tree.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
linux-imx-2.6.35.3: udev needs CONFIG_DEVTMPFS_MOUNT

New udev version needs CONFIG_DEVTMPFS_MOUNT to be selected, otherwise console
gets stuck.

The same approach has been already deployed into 3.0.35 as per commit 96417b88a
at meta-freescale-arm: (Recent versions of udev (182 in OE-core) need devtmpfs
to operate correctly).

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>