ARM: 7489/1: errata: fix workaround for erratum #720789 on UP systems

Commit 5a783cbc ("ARM: 7478/1: errata: extend workaround for erratum
 #720789") added workarounds for erratum #720789 to the range TLB
invalidation functions with the observation that the erratum only
affects SMP platforms. However, when running an SMP_ON_UP kernel on a
uniprocessor platform we must take care to preserve the ASID as the
workaround is not required.

This patch ensures that we don't set the ASID to 0 when flushing the TLB
on such a system, preserving the original behaviour with the workaround
disabled.

Cc: <stable@vger.kernel.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/tlb-v7.S

@@ -38,10 +38,10 @@ ENTRY(v7wbi_flush_user_tlb_range)
 	dsb
 	mov	r0, r0, lsr #PAGE_SHIFT		@ align address
 	mov	r1, r1, lsr #PAGE_SHIFT
-#ifdef CONFIG_ARM_ERRATA_720789
-	mov	r3, #0
-#else
 	asid	r3, r3				@ mask ASID
+#ifdef CONFIG_ARM_ERRATA_720789
+	ALT_SMP(W(mov)	r3, #0	)
+	ALT_UP(W(nop)		)
 #endif
 	orr	r0, r3, r0, lsl #PAGE_SHIFT	@ Create initial MVA
 	mov	r1, r1, lsl #PAGE_SHIFT