powerpc: Fix check for copy/paste instructions in alignment handler

Commit 07d2a628 ("powerpc/64s: Avoid cpabort in context switch
when possible", 2017-06-09) changed the definition of PPC_INST_COPY
and in so doing inadvertently broke the check for copy/paste
instructions in the alignment fault handler. The check currently
matches no instructions.

This fixes it by ANDing both sides of the comparison with the mask.

Fixes: 07d2a628 ("powerpc/64s: Avoid cpabort in context switch when possible")
Cc: stable@vger.kernel.org # v4.13+
Reported-by: NMarkus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: NPaul Mackerras <paulus@ozlabs.org>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/align.c

@@ -332,7 +332,7 @@ int fix_alignment(struct pt_regs *regs)
 	 * when pasting to a co-processor. Furthermore, paste_last is the
 	 * synchronisation point for preceding copy/paste sequences.
 	 */
-	if ((instr & 0xfc0006fe) == PPC_INST_COPY)
+	if ((instr & 0xfc0006fe) == (PPC_INST_COPY & 0xfc0006fe))
 		return -EIO;
 
 	r = analyse_instr(&op, regs, instr);