clk: renesas: rzg2l: Use FIELD_GET() for PLL register fields

clk: renesas: rzg2l: Use FIELD_GET() for PLL register fields

[ Upstream commit 72977f07b035e488c3f1928832a1616c6cae7278 ]

Use FIELD_GET() for PLL register fields.  This is its purpose.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230912045157.177966-14-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Stable-dep-of: a2b23159499e ("clk: renesas: rzg2l: Fix computation formula")
Signed-off-by: Sasha Levin <sashal@kernel.org>