bzip2/lzma: centralize format detection

Centralize the compression format detection to a common routine in the
lib directory, and use it for both initramfs and initrd.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/lib/Makefile b/lib/Makefile
index d9ac5a4..790de7c 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -11,7 +11,8 @@
 	 rbtree.o radix-tree.o dump_stack.o \
 	 idr.o int_sqrt.o extable.o prio_tree.o \
 	 sha1.o irq_regs.o reciprocal_div.o argv_split.o \
-	 proportions.o prio_heap.o ratelimit.o show_mem.o is_single_threaded.o
+	 proportions.o prio_heap.o ratelimit.o show_mem.o \
+	 is_single_threaded.o decompress.o
 
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
@@ -65,9 +66,9 @@
 obj-$(CONFIG_LZO_COMPRESS) += lzo/
 obj-$(CONFIG_LZO_DECOMPRESS) += lzo/
 
-obj-$(CONFIG_DECOMPRESS_GZIP) += decompress_inflate.o
-obj-$(CONFIG_DECOMPRESS_BZIP2) += decompress_bunzip2.o
-obj-$(CONFIG_DECOMPRESS_LZMA) += decompress_unlzma.o
+lib-$(CONFIG_DECOMPRESS_GZIP) += decompress_inflate.o
+lib-$(CONFIG_DECOMPRESS_BZIP2) += decompress_bunzip2.o
+lib-$(CONFIG_DECOMPRESS_LZMA) += decompress_unlzma.o
 
 obj-$(CONFIG_TEXTSEARCH) += textsearch.o
 obj-$(CONFIG_TEXTSEARCH_KMP) += ts_kmp.o