ARM: dts: stm32: Fix PHY post-reset delay on Avenger96

Per KSZ9031RNX PHY datasheet FIGURE 7-5: POWER-UP/POWER-DOWN/RESET TIMING
Note 2: After the de-assertion of reset, wait a minimum of 100 μs before
starting programming on the MIIM (MDC/MDIO) interface.

Add 1ms post-reset delay to guarantee this figure.

Fixes: 010ca9fe ("ARM: dts: stm32: Add missing ethernet PHY reset on AV96")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Patrick Delaunay <patrick.delaunay@foss.st.com>
Cc: linux-stm32@st-md-mailman.stormreply.com
To: linux-arm-kernel@lists.infradead.org
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>