In the case where CONFIG_PSTORE=n, the function efi_pstore_read() doesn't
have the correct list of parameters. This patch provides a definition
of efi_pstore_read() with 'char **buf' added to fix this warning:
"drivers/firmware/efivars.c:609: warning: initialization from".
problem introduced in commit 
f6f8285132907757ef84ef8dae0a1244b8cde6ac
Signed-off-by: Christoph Fritz <chf.fritz@googlemail.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
 }
 
 static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
-                              struct timespec *time, struct pstore_info *psi)
+                              struct timespec *timespec,
+                              char **buf, struct pstore_info *psi)
 {
        return -1;
 }