ARM: mx6: ddr: Make debug prints work with tiny printf

ARM: mx6: ddr: Make debug prints work with tiny printf

The %08X format returns just zeroes with tiny printf, which is
horribly confusing, especially when debugging DRAM calibration
problems. Change the format to %08x (with lowercase x), which
behaves correctly with either implementation of printf in SPL.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Eric Nelson <eric@nelint.com>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Reviewed-by: Eric Nelson <eric@nelint.com>