Commit 
58eb5b670747 ("pstore: fix crypto dependencies") fixed up the crypto
dependencies but missed the case when no compression is selected.
With CONFIG_PSTORE=y, CONFIG_PSTORE_COMPRESS=n  and CONFIG_CRYPTO=m we see
the following link error:
fs/pstore/platform.o: In function `pstore_register':
(.text+0x1b1): undefined reference to `crypto_has_alg'
(.text+0x205): undefined reference to `crypto_alloc_base'
fs/pstore/platform.o: In function `pstore_unregister':
(.text+0x3b0): undefined reference to `crypto_destroy_tfm'
Fix this by checking at compile-time if CONFIG_PSTORE_COMPRESS is enabled.
Fixes: 58eb5b670747 ("pstore: fix crypto dependencies")
Signed-off-by: Tobias Regnery <tobias.regnery@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
 
 static void allocate_buf_for_compression(void)
 {
-       if (!zbackend)
+       if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !zbackend)
                return;
 
        if (!crypto_has_comp(zbackend->name, 0, 0)) {
 
 static void free_buf_for_compression(void)
 {
-       if (!IS_ERR_OR_NULL(tfm))
+       if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && !IS_ERR_OR_NULL(tfm))
                crypto_free_comp(tfm);
        kfree(big_oops_buf);
        big_oops_buf = NULL;