arm64: mm: Adopt new alternative assembler macros

Convert the dynamic patching for ARM64_WORKAROUND_CLEAN_CACHE over to
the newly added alternative assembler macros.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/mm/cache.S

@@ -143,7 +143,12 @@ __dma_clean_range:
 	dcache_line_size x2, x3
 	sub	x3, x2, #1
 	bic	x0, x0, x3
-1:	alternative_insn "dc cvac, x0", "dc civac, x0", ARM64_WORKAROUND_CLEAN_CACHE
+1:
+alternative_if_not ARM64_WORKAROUND_CLEAN_CACHE
+	dc	cvac, x0
+alternative_else
+	dc	civac, x0
+alternative_endif
 	add	x0, x0, x2
 	cmp	x0, x1
 	b.lo	1b