ARM: pxa: correct errata number for PXA270

Comment incorrectly cites errata 39
    E39. SDIO: SDIO Devices Not Working at 19.5 Mbps

Should be errata 38
    E38. MEMC: Memory Controller hangs when entering Self Refresh Mode.
Signed-off-by: NAndrew Ruder <andrew.ruder@elecsyscorp.com>
Acked-by: NHaojian Zhuang <haojian.zhuang@linaro.org>

arch/arm/mach-pxa/sleep.S

@@ -157,7 +157,7 @@ pxa_cpu_do_suspend:
 	@ Do not reorder...
 	@ Intel PXA270 Specification Update notes problems performing
 	@ external accesses after SDRAM is put in self-refresh mode
-	@ (see Errata 39 ...hangs when entering self-refresh mode)
+	@ (see Errata 38 ...hangs when entering self-refresh mode)
 
 	@ force address lines low by reading at physical address 0
 	ldr	r3, [r2]