parisc: asm: psw.h: missing header guard

The psw.h header file contains #ifndef directive of the guard,
but the complimentary #define directive is missing. The patch
adds the appropriate #define to fix the header guard.
Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/include/asm/psw.h

 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _PARISC_PSW_H
-
+#define _PARISC_PSW_H
 
 #define	PSW_I	0x00000001
 #define	PSW_D	0x00000002