ARM: uniphier: move cmd_ddrmphy.c to fix build error

If CONFIG_CMD_DDRMPHY_DUMP is enabled, the build fails.

Fixes: 93d92d46cd01 ("ARM: uniphier: add dump command for DDR Multi PHY registers")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

diff --git a/arch/arm/mach-uniphier/cmd_ddrmphy.c b/arch/arm/mach-uniphier/dram/cmd_ddrmphy.c
similarity index 100%
rename from arch/arm/mach-uniphier/cmd_ddrmphy.c
rename to arch/arm/mach-uniphier/dram/cmd_ddrmphy.c