ppc: Move brg_clk to arch_global_data

Move this field into arch_global_data and tidy up.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/qe/fdt.c b/drivers/qe/fdt.c
index 73e9060..1a123b8 100644
--- a/drivers/qe/fdt.c
+++ b/drivers/qe/fdt.c
@@ -77,13 +77,13 @@
 	do_fixup_by_prop_u32(blob, "device_type", "qe", 4,
 		"bus-frequency", gd->qe_clk, 1);
 	do_fixup_by_prop_u32(blob, "device_type", "qe", 4,
-		"brg-frequency", gd->brg_clk, 1);
+		"brg-frequency", gd->arch.brg_clk, 1);
 	do_fixup_by_compat_u32(blob, "fsl,qe",
 		"clock-frequency", gd->qe_clk, 1);
 	do_fixup_by_compat_u32(blob, "fsl,qe",
 		"bus-frequency", gd->qe_clk, 1);
 	do_fixup_by_compat_u32(blob, "fsl,qe",
-		"brg-frequency", gd->brg_clk, 1);
+		"brg-frequency", gd->arch.brg_clk, 1);
 	do_fixup_by_compat_u32(blob, "fsl,qe-gtm",
 		"clock-frequency", gd->qe_clk / 2, 1);
 	fdt_fixup_qe_firmware(blob);