clk: renesas: rzv2h: Use both CLK_ON and CLK_MON bits for clock state validation

clk: renesas: rzv2h: Use both CLK_ON and CLK_MON bits for clock state validation

Update the clock enable/disable logic to follow the latest hardware
manual's guidelines, ensuring that both CLK_ON and CLK_MON bits are used
to confirm the clock state.

According to the manual, enabling a clock requires setting the
CPG_CLK_ON bit and verifying the clock has started using the CPG_CLK_MON
bit.  Similarly, disabling a clock requires clearing the CPG_CLK_ON bit
and confirming the clock has stopped via the CPG_CLK_MON bit.

Modify `rzv2h_mod_clock_is_enabled()` to check CLK_MON first and then
validate CLK_ON for a more accurate clock status evaluation.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20250407165202.197570-6-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>