cm-t35: various cleanups

Move #ifdef CONFIG_SMC911X out of board_eth_init() function,
simplify the board_mmc_init() function, and enclose handle_mac_address()
in the CONFIG_SMC911X.

Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>