clk: renesas: r8a08g045: Check the source of the CPU PLL settings

clk: renesas: r8a08g045: Check the source of the CPU PLL settings

On the RZ/G3S SoC, the CPU PLL settings can be set and retrieved through
the CPG_PLL1_CLK1 and CPG_PLL1_CLK2 registers.  However, these settings
are applied only when CPG_PLL1_SETTING.SEL_PLL1 is set to 0.
Otherwise, the CPU PLL operates at the default frequency of 1.1 GHz.
Hence add support to the PLL driver for returning the 1.1 GHz frequency
when the CPU PLL is configured with the default frequency.

Fixes: 01eabef547e6 ("clk: renesas: rzg2l: Add support for RZ/G3S PLL")
Fixes: de60a3ebe410 ("clk: renesas: Add minimal boot support for RZ/G3S SoC")
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20250115142059.1833063-1-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>