PPC 85xx: Add ELF entry point

We want to be able to directly execute the ELF binary without going
through the u-boot.bin one.

To know where we have to start executing this ELF binary  we have to
tell the linker where our entry point is.

Signed-off-by: Alexander Graf <agraf@suse.de>
Acked-by: Scott Wood <scottwood@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>

arch/powerpc/cpu/mpc85xx/u-boot.lds

@@ -13,6 +13,7 @@
 #endif
 
 OUTPUT_ARCH(powerpc)
+ENTRY(_start_e500)
 
 PHDRS
 {