dts: 2712: Update for device tree

dtoverlays: Fix up edt5406 entries to match with vc4-kms-dsi-7inch

vc4-kms-dsi-7inch expects the touch fragment to be named ts_i2c_frag,
but edt5406 didn't do this.

dt: Add DSI1 and DSI2 aliases to 2712

In order to keep the DRM names consistent as DSI-1 and DSI-2, add
aliases to the Pi5 DT.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>