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.

Fixes: 736d601fb38c ("dts: 2712: Update for device tree")

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>