board/freescale/imx8mqevk: remove hardware support section from readme

At first the support for i.MX8MQ processors was minimal, hence this
section in the readme file.

Since then, GPU support was added [1] in master and VPU in next [2].

So drop this section as it is confusing people and no one maintains it.

[1] https://git.buildroot.net/buildroot/commit/?id=84afda9c
[2] https://git.buildroot.net/buildroot/commit/?id=82732071



Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>