x86/asm/32: Remove a bunch of '& 0xffff' from pt_regs segment reads

Now that pt_regs properly defines segment fields as 16-bit on 32-bit
CPUs, there's no need to mask off the high word.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/mm/extable.c

@@ -142,7 +142,7 @@ void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
 	 * undefined.  I'm not sure which CPUs do this, but at least
 	 * the 486 DX works this way.
 	 */
-	if ((regs->cs & 0xFFFF) != __KERNEL_CS)
+	if (regs->cs != __KERNEL_CS)
 		goto fail;
 
 	/*