bzip2/lzma/gzip: pre-boot malloc doesn't return NULL on failure

The trivial malloc implementation used in the pre-boot environment by the
decompressors returns a bad pointer on failure (falling through after
calling error).  This is doubly wrong - the callers expect malloc to
return NULL on failure, second the error function is intended to be
used by the decompressors to propagate errors to *their* callers.  The
decompressors have no access to any state set by the error function.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
LKML-Reference: <4b26b1ef.hIInb2AYPMtImAJO%phillip@lougher.demon.co.uk>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>