ipq806x: Bring missing patches from 5.4 to 5.10

ipq806x: Bring missing patches from 5.4 to 5.10

Kernel 5.10 support for ipq806x was added at the same time that these
patches were developed for kernel 5.4. This carries the patches forward
to kernel 5.10.

fa731838c524 ipq806x: dwmac: clear forced speed during probe
75ca641f1b84 ipq806x: Add "snps,dwmac" to all gmac compatible=
d62825dd77b3 ipq806x: dwmac: set forced speed when using fixed-link

Signed-off-by: Mark Mentovai <mark@moxienet.com>
Run-tested: ipq806x/ubnt,unifi-ac-hd
Cc: Ansuel Smith <ansuelsmth@gmail.com>