2d-primitives: fix no previous prototype warning ...

Fix the following warnings:

lib/gui/2d-primitives.c:88:6: warning: no
previous prototype for ‘gu_draw_line’ [-Wmissing-prototypes]
 void gu_draw_line(struct screen *sc,
      ^~~~~~~~~~~~
lib/gui/2d-primitives.c:174:6: warning: no
previous prototype for ‘gu_draw_circle’ [-Wmissing-prototypes]
 void gu_draw_circle(struct screen *sc,
      ^~~~~~~~~~~~~~

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

2d-primitives: fix typos in function names in comments ...

This fixes gl_* -> gu_* in several places.

Reported-by: Chris Healy <cphealy@gmail.com>
Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

2d-primitives: fix missing pixel in gu_draw_line() ...

When drawing line from (x1, y1) to (x2, y2), pixel at (x2, y2) should
be included.

Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Tested-by: Chris Healy <[1]cphealy@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

2d-primitives: check dimensions in __illuminate ...

gl_draw_circle draws outside of the screen if the resolution is too low.
This lead to memory corruption. Check the dimensions before drawing.

Signed-off-by: Bastian Stender <bst@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

GUI: Add code to draw simple graphics ...

Add code to draw simple graphics, namely lines(solid or dashed) and
circles.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>