clk: renesas: r8a77970: Add Z2 clock

Add support for the Z2 (Cortex-A53 System CPU) clock on R-Car V3M, which
uses a fixed SYS-CPU divider.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/6a9169e5bc92c2b9549292769a0814e04b9147cf.1676560357.git.geert+renesas@glider.be

drivers/clk/renesas/r8a77970-cpg-mssr.c

@@ -76,6 +76,7 @@ static const struct cpg_core_clk r8a77970_core_clks[] __initconst = {
 	DEF_FIXED(".pll1_div4",	CLK_PLL1_DIV4,	CLK_PLL1_DIV2,	2, 1),
 
 	/* Core Clock Outputs */
+	DEF_FIXED("z2",		R8A77970_CLK_Z2,    CLK_PLL1_DIV4,  1, 1),
 	DEF_FIXED("ztr",	R8A77970_CLK_ZTR,   CLK_PLL1_DIV2,  6, 1),
 	DEF_FIXED("ztrd2",	R8A77970_CLK_ZTRD2, CLK_PLL1_DIV2, 12, 1),
 	DEF_FIXED("zt",		R8A77970_CLK_ZT,    CLK_PLL1_DIV2,  4, 1),