reiserfs: fix __RASSERT format string

__RASSERT format string does not use the PID argument.  reiserfs_panic
arguments are therefore formatted with the wrong format specifier (for
example __LINE__ with %s).  This bug was introduced when commit
c3a9c210

 ("reiserfs: rework reiserfs_panic") removed a
"reiserfs[%i]" prefix.

This bug is only triggered when using CONFIG_REISERFS_CHECK, otherwise
__RASSERT is never used.

Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Acked-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Jan Kara <jack@suse.cz>