math_utils: add NGLI_CEIL_RSHIFT
math_utils: add NGLI_CEIL_RSHIFT

Right-shift "division" with ceiling rounding, useful for chroma
subsampling in video codecs.

gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl