UBUNTU: SAUCE: powerpc: use sync instead of hwsync mnemonic

CVE-2017-5754

hwsync was added as a mnemonic for sync in binutils 2.25, prior
to that there is no support for hwsync. Replace uses of hwsync
with sync to maintain compatibility with older binutils.

Fixes: ee71154e ("UBUNTU: SAUCE: rfi-flush: Add barriers to the fallback L1D flushing")
Acked-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

arch/powerpc/kernel/exceptions-64s.S

@@ -743,7 +743,7 @@ rfi_flush_fallback:
 	DCBT_STOP_ALL_STREAM_IDS(r11) /* Stop prefetch streams */
 
 	/* order ld/st prior to dcbt stop all streams with flushing */
-	hwsync
+	sync
 1:	li	r8,0
 	.rept	8 /* 8-way set associative */
 	ldx	r11,r10,r8
@@ -785,7 +785,7 @@ hrfi_flush_fallback:
 	DCBT_STOP_ALL_STREAM_IDS(r11) /* Stop prefetch streams */
 
 	/* order ld/st prior to dcbt stop all streams with flushing */
-	hwsync
+	sync
 1:	li	r8,0
 	.rept	8 /* 8-way set associative */
 	ldx	r11,r10,r8