ARM: dts: vfxxx: Include support for dspi[23] functionality.

Extend the existing Vybrid DSPI devicetree implementation to also
describe the dspi2 and dspi3 functional blocks.

Signed-off-by: Cory Tusar <cory.tusar@pid1solutions.com>
Acked-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>