net: ethernet: stmmac: dwmac-rk: fix bulk clock leak when the PHY clock fails

gmac_clk_enable() enables the bulk clocks first and then the optional
PHY clock. If clk_prepare_enable() on the PHY clock fails, the function
returns without rolling back the bulk clocks, and bsp_priv->clk_enabled
stays false, so the later gmac_clk_enable(bsp_priv, false) becomes a
no-op and the bulk clock references are leaked.

Add the missing clk_bulk_disable_unprepare() on that failure path.

Fixes: ea449f7fa0bf ("net: ethernet: stmmac: dwmac-rk: rework optional clock handling")
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>
Signed-off-by: Coia Prant <coiaprant@gmail.com>
Link: https://patch.msgid.link/20260923123713.3137146-1-coiaprant@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>