It is not safe to compare timer values directly.

On 32-bit systems, for example, timer_get_us() wraps around every
72 min. (2 ^ 32 / 1000000 =~ 4295 sec =~ 72 min).  Depending on
the get_ticks() implementation, it may wrap more frequently.
The 72 min might be possible on the use of U-Boot.

Let's borrow time_after, time_before, and friends to solve the
wrap-around problem.

These macros were copied from include/linux/jiffies.h of Linux 4.9.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

The include/common.h is a collection of unrelated declarations,
macros, etc.

It is horrible to include such a cluttered header just for some
timer functions.  Split out timer functions into include/time.h.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>