clk: rockchip: Drop empty init callback for rk3588 PLL type

clk: rockchip: Drop empty init callback for rk3588 PLL type

Unlike PLLs in previous geneation of SoCs, PLLs in RK3588 type don't
require any platform-specific initialization. Drop callback
rockchip_rk3588_pll_init() that does nothing in fact to clean the
driver up.

Signed-off-by: Yao Zi <ziyao@disroot.org>
Link: https://lore.kernel.org/r/20250326113556.21039-1-ziyao@disroot.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>