ARM: keystone: ddr3: workaround for ddr3a/3b memory issue

This patch implements a workaround to fix DDR3 memory issue.
The code for workaround detects PGSR0 errors and then preps for
and executes a software-controlled hard reset.In board_early_init,
where logic has been added to identify whether or not the previous
reset was a PORz. PLL initialization is skipped in the case of a
software-controlled hard reset.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Keegan Garcia <kgarcia@ti.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>