libsdl: Clean up configure option QA warnings

libsdl: Clean up configure option QA warnings

WARNING: QA Issue: nativesdk-libsdl: configure was passed unrecognised options: --disable-video-gem --disable-video-xbios --enable-dlopen --disable-debug --enable-endian

The gem and xbios options exist but their helptext is wrong and there
is no "video" in the name. This patch removes the now obsolete options
and corrects the names of the others to match reality.

(From OE-Core rev: 8cea5dd7d6804a8d739f5db6a5814ab6c802d538)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>