ARM: socfpga: Add boot trampoline for Arria10

The Arria10 uses slightly different boot image header than the Gen5 SoCs,
in particular the header itself contains an offset from the start of the
header to which the Arria10 jumps. This offset must not be negative, yet
the header is placed at offset 0x40 of the bootable binary. Therefore, to
jump into U-Boot, add a trampoline just past the Arria10 boot header and
point to this trampoline at fixed offset from the header generated using
the mkimage -T socfpgaimage_v1 . Note that it is not needed to jump back
to offset 0x0 of the image, it is possible to jump directly at the reset
label and save processing two instructions.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Chin Liang See <chin.liang.see@intel.com>

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

@@ -17,8 +17,8 @@ _start:
 	.word	0xcafec0d3;	/* Checksum, zero-pad */
 	nop;
 
-	b reset;		/* SoCFPGA jumps here */
-	nop;
+	b reset;		/* SoCFPGA Gen5 jumps here */
+	b reset;		/* SoCFPGA Gen10 trampoline */
 	nop;
 	nop;
 #endif