lib: time: Add microsecond timer

Add get_timer_us(), which is useful e.g. when we need higher
precision timestamps.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Tom Rini <trini@konsulko.com>
Cc: Simon Glass <sjg@chromium.org>
[trini: Fixup arch/arm/mach-bcm283x/include/mach/timer.h]
Signed-off-by: Tom Rini <trini@konsulko.com>
3 files changed