sparse: Refactor chunk parsing function

sparse: Refactor chunk parsing function

The chunk parsing code was duplicating a lot of code among the various
chunk types, while all of them could be covered by generic and simple
functions.

Refactor the current code to reuse as much code as possible and hopefully
make the chunk parsing loop more readable and concise.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Tom Rini <trini@konsulko.com>