ARM: DRA7: emif: Fix DDR init sequence during warm reset

ARM: DRA7: emif: Fix DDR init sequence during warm reset

Commit (20fae0a - ARM: DRA7: DDR: Enable SR in Power Management Control)
enables Self refresh mode by default and during warm reset the EMIF
contents are preserved. After warm reset EMIF sees that it is idle and
puts DDR in self-refresh. When in SR, leveling operations cannot be done
as DDR can only accept SR exit command, so its hanging during warm reset.
In order to fix this reset the power management control register before
EMIF initialization if it is a warm reset.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>