Rename reset to sysreset

The current reset API implements a method to reset the entire system.
In the near future, I'd like to introduce code that implements the device
tree reset bindings; i.e. the equivalent of the Linux kernel's reset API.
This controls resets to individual HW blocks or external chips with reset
signals. It doesn't make sense to merge the two APIs into one since they
have different semantic purposes. Resolve the naming conflict by renaming
the existing reset API to sysreset instead, so the new reset API can be
called just reset.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>