Correct SPL use of SYS_FSL_ERRATUM_A010539

This converts 1 usage of this option to the non-SPL form, since there is
no SPL_SYS_FSL_ERRATUM_A010539 defined in Kconfig

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/cpu/armv8/fsl-layerscape/cpu.c b/arch/arm/cpu/armv8/fsl-layerscape/cpu.c
index b0e8678..12d3118 100644
--- a/arch/arm/cpu/armv8/fsl-layerscape/cpu.c
+++ b/arch/arm/cpu/armv8/fsl-layerscape/cpu.c
@@ -760,7 +760,7 @@
 	}
 #endif
 
-	if (CONFIG_IS_ENABLED(SYS_FSL_ERRATUM_A010539) && !rcw_src)
+	if (IS_ENABLED(CONFIG_SYS_FSL_ERRATUM_A010539) && !rcw_src)
 		src = BOOT_SOURCE_QSPI_NOR;
 
 	debug("%s: src 0x%x\n", __func__, src);