dra72_evm: Switch to DM_SERIAL

Tested on J6Eco EVM.
Signed-off-by: Tom Rini <trini@konsulko.com>
Tested-by: Lokesh Vutla <lokeshvutla@ti.com>

configs/dra72_evm_defconfig

 CONFIG_ARM=y
 CONFIG_OMAP54XX=y
+CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_TARGET_DRA7XX_EVM=y
+CONFIG_DM_SERIAL=y
 CONFIG_DM_GPIO=y
+CONFIG_SPL_STACK_R_ADDR=0x82000000
 CONFIG_DEFAULT_DEVICE_TREE="dra72-evm"
 CONFIG_SPL=y
 CONFIG_SPL_STACK_R=y
-CONFIG_SPL_STACK_R_ADDR=0x82000000
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set
 # CONFIG_CMD_SETEXPR is not set