armv8/ls2085a: Increase the supported kernel size

Increases the kernel size supported for LS2085A platforms:-
 - Update environment variables
 - Add ramdisk_size in bootargs env variable
 - Define  CONFIG_SYS_BOOTM_LEN to 64MB

Signed-off-by: Bhupesh Sharma <bhupesh.sharma at freescale.com>
Signed-off-by: Prabhakar Kushwaha <prabhakar at freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>