clk: shmobile: mstp: Consider "zb_clk" suitable for power management

Currently the CPG/MSTP Clock Domain code looks for MSTP clocks to power
manage a device.

Unfortunately, on R-Mobile APE6 (r8a73a4) and SH-Mobile AG5 (sh73a0),
the Bus State Controller (BSC) is not power-managed by an MSTP clock,
but by a plain CPG clock (zb_clk).  Add a special case to handle this,
so the clock is properly managed, and devices connected to the BSC work
as expected.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

drivers/clk/shmobile/clk-mstp.c

@@ -259,6 +259,10 @@ int cpg_mstp_attach_dev(struct generic_pm_domain *domain, struct device *dev)
 					    "renesas,cpg-mstp-clocks"))
 			goto found;
 
+		/* BSC on r8a73a4/sh73a0 uses zb_clk instead of an mstp clock */
+		if (!strcmp(clkspec.np->name, "zb_clk"))
+			goto found;
+
 		of_node_put(clkspec.np);
 		i++;
 	}