linux-raspberrypi-5.10: remove since they have unavailable devicetree's

[quaresmajose]

The imx708.dtbo and bcm2711-rpi-cm4s.dtb is not available on the this kernel:

# | make[2]: *** No rule to make target 'arch/arm64/boot/dts/overlays/imx708.dtbo'.  Stop.
# | make[2]: *** No rule to make target 'arch/arm64/boot/dts/broadcom/bcm2711-rpi-cm4s.dtb'.  Stop.

- What I did

- How I did it

[quaresmajose]

This will also fail when generating the wic image so the right fix is backporting the dtb's

| output: install: cannot stat '/build/deploy/images/raspberrypi4-64/imx708.dtbo': No such file or directory

[quaresmajose]

The overlays/imx708.dtbo is not supported and backport [1] the dtbo is not accepted so drop this kernel version. [1] https://github.com/raspberrypi/linux/pull/5452

[agherzan]

I am happy to drop this version from master.

[quaresmajose]

I am happy to drop this version from master.

I deleted them from my layer some time ago.