ntfs: remove redundant initialization to pointer cb_sb_start

The pointer cb_sb_start is being initialized with a value that is never
read, it is being re-assigned the same value later on when it is first
being used. The initialization is redundant and can be removed.

Cleans up clang scan build warning:
fs/ntfs/compress.c:164:6: warning: Value stored to 'cb_sb_start' during its initialization is never read [deadcode.DeadStores]
        u8 *cb_sb_start = cb;   /* Beginning of the current sb in the cb. */

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Message-Id: <20230418153607.3125704-1-colin.i.king@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>