math.h: Add unsigned 8 bits fractional numbers type

Some users may be requiring only rather small numbers as both
numerator and denominator: add signed and unsigned 8 bits
structs {s8,u8}_fract.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://patch.msgid.link/20240604123008.327424-4-angelogioacchino.delregno@collabora.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>