When U-Boot started using SPDX tags we were among the early adopters and
there weren't a lot of other examples to borrow from.  So we picked the
area of the file that usually had a full license text and replaced it
with an appropriate SPDX-License-Identifier: entry.  Since then, the
Linux Kernel has adopted SPDX tags and they place it as the very first
line in a file (except where shebangs are used, then it's second line)
and with slightly different comment styles than us.

In part due to community overlap, in part due to better tag visibility
and in part for other minor reasons, switch over to that style.

This commit changes all instances where we have a single declared
license in the tag as both the before and after are identical in tag
contents.  There's also a few places where I found we did not have a tag
and have introduced one.

Signed-off-by: Tom Rini <trini@konsulko.com>

Add a sandbox I2C emulation device which emulates a real-time clock. The
clock works off an offset from the current system time, and supports setting
and getting the clock, as well as access to byte-width regisers in the RTC.
It does not support changing the system time.

This device can be used for testing the 'date' command on sandbox, as well
as the RTC uclass.

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