[PATCH] btrfs: Fix build error while LIBCRC32C is module

[YueHaibing]

If CONFIG_BTRFS_FS is y and CONFIG_LIBCRC32C is m,
building fails:

fs/btrfs/super.o: In function `btrfs_mount_root':
super.c:(.text+0xb7f9): undefined reference to `crc32c_impl'
fs/btrfs/super.o: In function `init_btrfs_fs':
super.c:(.init.text+0x3465): undefined reference to `crc32c_impl'
fs/btrfs/extent-tree.o: In function `hash_extent_data_ref':
extent-tree.c:(.text+0xe60): undefined reference to `crc32c'
extent-tree.c:(.text+0xe78): undefined reference to `crc32c'
extent-tree.c:(.text+0xe8b): undefined reference to `crc32c'
fs/btrfs/dir-item.o: In function `btrfs_insert_xattr_item':
dir-item.c:(.text+0x291): undefined reference to `crc32c'
fs/btrfs/dir-item.o: In function `btrfs_insert_dir_item':
dir-item.c:(.text+0x429): undefined reference to `crc32c'

Select LIBCRC32C to fix it.

Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Fixes: d5178578bcd4 ("btrfs: directly call into crypto framework for checksumming")
Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
---
 fs/btrfs/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/btrfs/Kconfig b/fs/btrfs/Kconfig
index 2521a24..df4041d 100644
--- a/fs/btrfs/Kconfig
+++ b/fs/btrfs/Kconfig
@@ -4,6 +4,7 @@ config BTRFS_FS
 	tristate "Btrfs filesystem support"
 	select CRYPTO
 	select CRYPTO_CRC32C
+	select LIBCRC32C
 	select CRYPTO_SHA256
 	select ZLIB_INFLATE
 	select ZLIB_DEFLATE
-- 
2.7.4