bzip2/lzma: don't stop search at first unconfigured compression

Impact: Bugfix, avoids kernels which build but panic on boot

Fix a bug in decompress.c : only scanned until the first
non-configured compressor (with disastrous result especially if that
was gzip.)

Signed-off-by: Alain Knaff <alain@knaff.lu>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>