armv8: ls1046ardb: SPL size reduction

Using changes in this patch we were able to reduce approx 4k
size of u-boot-spl.bin image. Following is breif description of
changes to reduce SPL size:
1. Changes in board/freescale/ls1046ardb/Makefile to remove
   compilation of eth.c and cpld.c in case of SPL build.
2. Changes in board/freescale/ls1046ardb/ls1046ardb.c to keep
   only ddr_init and board_early_init_f funcations in case of SPL
   build.
3. Changes in ls1046a_common.h & ls1046ardb.h to remove driver
   specific macros due to which static data was being compiled in
   case of SPL build.
4. Disable MMC driver from bieng compiled in case of SPL NAND
   build and NAND driver from bieng compiled in case of SPL MMC build.

Signed-off-by: Vinitha Pillai <vinitha.pillai@nxp.com>
Signed-off-by: Sumit Garg <sumit.garg@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>