mesa: make ligles3-dev RDEPENDS on libgles2-dev

mesa: make ligles3-dev RDEPENDS on libgles2-dev

Khronos documentation[1] says that include/GLES2/gl2ext.h can be used
for OpenGL ES 3 specification as well as for OpenGL ES 2.
There can be applications including GLES2/gl2ext.h instead of
GLES3/gl3ext.h meaning we should probably bring in GLES2/gl2ext.h if
someone asks for development package of libgles3.

[1] https://www.khronos.org/registry/OpenGL/index_es.php#headers

Cc: Quentin Schulz <foss+yocto@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>