board

CONFIG_SYS_CONFIG_NAME is not proper config option for different low
level init files because different board revisions requires different
psu_init_gpl* files.

Also at the end of moving drivers to DM all board specific configuration
files should be removed.

The same changes was done for Zynq.
"ARM: zynq: Simplify zynq configuration"
(sha1: ad5b5801)

Signed-off-by: Michal Simek <michal.simek@xilinx.com>