kselftest/arm64: Add a TODO list for floating point tests

Write down some ideas for additional coverage for floating point in case
someone feels inspired to look into them.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Link: https://lore.kernel.org/r/20210803140450.46624-5-broonie@kernel.org


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>