configs: am335x_pdu001: remove CONFIG_DM_I2C_COMPAT

Remove the last call to the non-DM I2C API.
Also remove the #undef CONFIG_DM_I2C_COMPAT because it is not defined
in the common header file anymore.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Felix Brack <fb@ltec.ch>
Tested-by: Felix Brack <fb@ltec.ch>
Reviewed-by: Heiko Schocher <hs@denx.de>