pstore: Fix flags to enable dumps on powerpc

After commit c950fd6f20 kernel registers pstore write based on flag set.
Pstore write for powerpc is broken as flags(PSTORE_FLAGS_DMESG) is not set for
powerpc architecture. On panic, kernel doesn't write message to
/fs/pstore/dmesg*(Entry doesn't gets created at all).

This patch enables pstore write for powerpc architecture by setting
PSTORE_FLAGS_DMESG flag.

Fixes: c950fd6f20 ("pstore: Split pstore fragile flags")
Cc: stable@vger.kernel.org # v4.9+
Signed-off-by: Ankit Kumar <ankit@linux.vnet.ibm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

arch/powerpc/kernel/nvram_64.c

@@ -547,6 +547,7 @@ static ssize_t nvram_pstore_read(struct pstore_record *record)
 static struct pstore_info nvram_pstore_info = {
 	.owner = THIS_MODULE,
 	.name = "nvram",
+	.flags = PSTORE_FLAGS_DMESG,
 	.open = nvram_pstore_open,
 	.read = nvram_pstore_read,
 	.write = nvram_pstore_write,