libsdl2: upgrade 2.30.6 -> 2.30.7

ChangeLog:
https://github.com/libsdl-org/SDL/releases/tag/release-2.30.7



* Added support for the Retro-bit Controller in PS3 mode
* Fixed the cursor becoming visible when using relative mode under
  XWayland
* Fixed DRM initialization failure on some Linux systems
* Fixed a crash when the current mouse capture window is destroyed

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>