arm: spl: Add I2C linker list in generic .lds

On LS1, DDR is initialized by reading SPD through I2C interface
in SPL code. For I2C, ll_entry_count() is called, and it returns
the number of elements of a linker-generated array placed into
subsection of .u_boot_list section specified by _list argument.
So add I2C linker list in the generic .lds to fix the issue about
using I2C in SPL.

Signed-off-by: Alison Wang <alison.wang@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>

arch/arm/cpu/u-boot-spl.lds

@@ -32,6 +32,9 @@ SECTIONS
 	}
 
 	. = ALIGN(4);
+	.u_boot_list : {
+		KEEP(*(SORT(.u_boot_list*_i2c_*)));
+	}
 
 	. = .;
 #ifdef CONFIG_SPL_DM