armv8: fsl-layerscape: Support loading 32-bit OS with PSCI enabled

As PSCI and secure monitor firmware framework are enabled, this patch is
to support loading 32-bit OS in such case. The default target exception
level returned to U-Boot is EL2, so the corresponding work to switch to
AArch32 EL2 and jump to 32-bit OS are done in U-Boot and secure firmware
together.

Signed-off-by: Alison Wang <alison.wang@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
index 287ff5c..01efc43 100644
--- a/arch/arm/include/asm/system.h
+++ b/arch/arm/include/asm/system.h
@@ -215,6 +215,8 @@
  */
 void armv8_switch_to_el1(u64 args, u64 mach_nr, u64 fdt_addr,
 			 u64 entry_point, u64 es_flag);
+void armv8_el2_to_aarch32(u64 args, u64 mach_nr, u64 fdt_addr,
+			  u64 entry_point);
 void gic_init(void);
 void gic_send_sgi(unsigned long sgino);
 void wait_for_wakeup(void);