ARM: k2g: Program DDR PHY MR2 register with the default value

ARM: k2g: Program DDR PHY MR2 register with the default value

K2G GP doesn't require the MR2 register to be programed since the
default is good enough. However, newer K2G boards do need to change
this register value. Therefore, instead of not writing this register if
ran on a K2G board just program the value to be written to match the
default/reset value.

Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>