ppc: arm: Move sdhc_clk into arch_global_data

This is used by both powerpc and arm, but I think it still qualifies as
architecture-specific.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/powerpc/cpu/mpc85xx/speed.c b/arch/powerpc/cpu/mpc85xx/speed.c
index 7173c07..297f2ed 100644
--- a/arch/powerpc/cpu/mpc85xx/speed.c
+++ b/arch/powerpc/cpu/mpc85xx/speed.c
@@ -428,9 +428,9 @@
 #if defined(CONFIG_FSL_ESDHC)
 #if defined(CONFIG_MPC8569) || defined(CONFIG_P1010) ||\
        defined(CONFIG_P1014)
-	gd->sdhc_clk = gd->bus_clk;
+	gd->arch.sdhc_clk = gd->bus_clk;
 #else
-	gd->sdhc_clk = gd->bus_clk / 2;
+	gd->arch.sdhc_clk = gd->bus_clk / 2;
 #endif
 #endif /* defined(CONFIG_FSL_ESDHC) */