socfpga: boot0 hook: adjust to unified boot0 semantics

With the updated boot0 semantics (i.e. giving the boot0-hook control
over when and where the vector table is emitted), the boot0-hook for
the socfpga needs to be adjusted.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

arch/arm/mach-socfpga/include/mach/boot0.h

@@ -7,6 +7,9 @@
 #ifndef __BOOT0_H
 #define __BOOT0_H
 
+_start:
+	ARM_VECTORS
+
 #ifdef CONFIG_SPL_BUILD
 	.balignl 64,0xf33db33f;