avr32: Move cpu_hz 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/arch/avr32/lib/bootm.c b/arch/avr32/lib/bootm.c
index 74ebeca..87f3f9c 100644
--- a/arch/avr32/lib/bootm.c
+++ b/arch/avr32/lib/bootm.c
@@ -109,7 +109,7 @@
 	params->hdr.size = tag_size(tag_clock);
 	params->u.clock.clock_id = ACLOCK_BOOTCPU;
 	params->u.clock.clock_flags = 0;
-	params->u.clock.clock_hz = gd->cpu_hz;
+	params->u.clock.clock_hz = gd->arch.cpu_hz;
 
 #ifdef CONFIG_AT32AP7000
 	/*