uboot-phytec

stm32f7: remove not needed configuration from board config

This patch removes:
	- CONFIG_CMD_MEM: enabled by default
	- CONFIG_DESIGNWARE_ETH : not being used anywhere.

Signed-off-by: Vikas Manocha <vikas.manocha@st.com>
cc: Christophe KERELLO <christophe.kerello@st.com>