armv8: layerscape: don't initialize GIC in SPL

The BL31 expects the GIC to be uninitialized. Thus, if we are loading
the BL31 by the SPL we must not initialize it. If u-boot is loaded by
the SPL directly, it will initialize the GIC again (in the same
lowlevel_init()).

This was tested on a custom board with SPL loading the BL31 and jumping
to u-boot as BL33 as well as loading u-boot directly by the SPL. In case
the ATF BL1/BL2 is used, this patch won't change anything, because no
SPL is used at all.

Signed-off-by: Michael Walle <michael@walle.cc>
diff --git a/arch/arm/cpu/armv8/fsl-layerscape/lowlevel.S b/arch/arm/cpu/armv8/fsl-layerscape/lowlevel.S
index a519f6e..d880373 100644
--- a/arch/arm/cpu/armv8/fsl-layerscape/lowlevel.S
+++ b/arch/arm/cpu/armv8/fsl-layerscape/lowlevel.S
@@ -192,6 +192,7 @@
 #endif
 
 	/* Initialize GIC Secure Bank Status */
+#if !defined(CONFIG_SPL_BUILD)
 #if defined(CONFIG_GICV2) || defined(CONFIG_GICV3)
 	branch_if_slave x0, 1f
 	bl	get_gic_offset
@@ -205,6 +206,7 @@
 	bl	gic_init_secure_percpu
 #endif
 #endif
+#endif
 
 100:
 	branch_if_master x0, x1, 2f