bootstage: arm: Add bootstage calls in board and bootm

Add calls to bootstage before and after relocation, and just
before jumping to the OS.

The idea here is you can call bootstage_report() to get a report.
Additionally, if you define CONFIG_BOOTSTAGE_REPORT then a report is
printed automatically by U-Boot just before jumping to the kernel.

Signed-off-by: Simon Glass <sjg@chromium.org>