stm32mp1: ram: remove the support of calibration result

The support of a predefined DDR PHY tuning result is removed for
STM32MP1 driver because it is not needed at the supported frequency
when built-in calibration is executed.

The calibration parameters were provided in the device tree by the
optional node "st,phy-cal", activated in ddr helper file by the
compilation flag DDR_PHY_CAL_SKIP and filled with values generated
by the CubeMX DDR utilities.

This patch
- updates the binding file to remove "st,phy-cal" support
- updates the device trees and remove the associated defines
- simplifies the STM32MP1 DDR driver and remove the support of
  the optional parameter "st,phy-cal"

After this patch, the built-in calibration is always executed
and the calibration registers are moved in the phy dynamic part;
that allows manual tests.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>