decompressors: Use malloc/free wrappers ...

The decompressors are used both in a regular image and also for image
decompression. Both need different malloc implementations. Using
malloc/free directly in the decompressor code easily leads to include
file conflicts, so use MALLOC/FREE which can be defined correctly for
the two different usecases.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Unused files removed ...

Files "modules.builtin" probably have been copied from kernel tree.
This files not used by barebox and can be removed safely.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

add kernel gunzip implementation ...

The kernel uncompression functions have a unified API so use this
implementation to get it.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>