clk: renesas: rcar-gen3: Remove superfluous masking in cpg_z_clk_set_rate()

Due to the clamping of mult, "(32 - mult) << __ffs(zclk->mask)" can
never exceed the mask.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/20210326120100.1577596-4-geert+renesas@glider.be

drivers/clk/renesas/rcar-gen3-cpg.c

@@ -104,8 +104,7 @@ static int cpg_z_clk_set_rate(struct clk_hw *hw, unsigned long rate,
 	if (readl(zclk->kick_reg) & CPG_FRQCRB_KICK)
 		return -EBUSY;
 
-	cpg_reg_modify(zclk->reg, zclk->mask,
-		       ((32 - mult) << __ffs(zclk->mask)) & zclk->mask);
+	cpg_reg_modify(zclk->reg, zclk->mask, (32 - mult) << __ffs(zclk->mask));
 
 	/*
 	 * Set KICK bit in FRQCRB to update hardware setting and wait for