ARM: dts: imx6-display5: replace marvell,88E1510 with ethernet-phy-ieee802.3-c22

ARM: dts: imx6-display5: replace marvell,88E1510 with ethernet-phy-ieee802.3-c22

Replace the vendor-specific PHY compatible string with the generic
ethernet-phy-ieee802.3-c22 compatible.

The marvell,88E1510 compatible is listed in whitelist_phys[] and is
never matched against a PHY driver. PHY devices are expected to use
the generic ethernet-phy-ieee802.3-c22 compatible unless a specific
MDIO driver match is required.

The 88E1510 is compatible with Clause 22 PHY devices, so use the
generic compatible string instead.

Fix below CHECK_DTBS warnings:
arch/arm/boot/dts/nxp/imx/imx6q-display5-tianma-tm070-1280x768.dtb: /soc/bus@2100000/ethernet@2188000/mdio/ethernet-phy@0: failed to match any schema with compatible: ['marvell,88E1510']

Known other user (uboot) did not use marvell,88E1510.

Signed-off-by: Frank Li <Frank.Li@nxp.com>