dt-bindings: phy: uniphier-ahci: Fix missing reset-names

UniPhier AHCI PHY controller needs to specify 6 reset lines, so this adds
missing "phy" to reset-names and increases maxItems of resets.

Fixes: 34f92b67

 ("dt-bindings: phy: uniphier-ahci: Add bindings for Pro4 SoC")
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/1648637715-19262-4-git-send-email-hayashi.kunihiko@socionext.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>