x86/entry/32: Add missing ASM_CLAC to general_protection entry

All exception entry points must have ASM_CLAC right at the
beginning. The general_protection entry is missing one.

Fixes: e59d1b0a ("x86-32, smap: Add STAC/CLAC instructions to 32-bit kernel entry")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200225220216.219537887@linutronix.de

arch/x86/entry/entry_32.S

@@ -1694,6 +1694,7 @@ SYM_CODE_START(int3)
 SYM_CODE_END(int3)
 
 SYM_CODE_START(general_protection)
+	ASM_CLAC
 	pushl	$do_general_protection
 	jmp	common_exception
 SYM_CODE_END(general_protection)