net: stmmac: dwmac-generic: add missing compatible strings

net: stmmac: dwmac-generic: add missing compatible strings

devicetree binding for stmmac states:
- compatible: Should be "snps,dwmac-<ip_version>", "snps,dwmac"
	For backwards compatibility: "st,spear600-gmac" is also supported.

Since dwmac-generic.c calls stmmac_probe_config_dt explicitly,
another alternative would have been to remove all compatible strings
other than "snps,dwmac" and "st,spear600-gmac" from dwmac-generic.c.

However, that would probably do more good than harm, since when trying
to figure out what hardware a certain driver supports, you usually look
at the compatible strings in the struct of_device_id, and not in some
function defined in a completely different file.

No functional change intended.

Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>