arm: at91: arm926ejs/u-boot-spl.lds: Add _image_binary_end to SPL lds

This patch adds _image_binary_end to the SPL linker script. This will be
used be the upcoming GARDENA AT91SAM based platform, which uses DT in
SPL and configures CONFIGURE_SPL_SEPARATE_BSS.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Heiko Schocher <hs@denx.de>
Cc: Andreas Bießmann <andreas@biessmann.org>
Cc: Eugen Hristev <eugen.hristev@microchip.com>
Reviewed-by: Heiko Schocher <hs@denx.de>

arch/arm/mach-at91/arm926ejs/u-boot-spl.lds

@@ -39,6 +39,8 @@ SECTIONS
 		*(.__end)
 	} >.sram
 
+	_image_binary_end = .;
+
 	.bss :
 	{
 		. = ALIGN(4);