[U-Boot] [RFC] mmc:saveenv problem

[Song, Elen]

Hello Dear Andy:
	I found in env_mmc.c, mmc_get_env_addr(...)only do *env_addr = CONFIG_ENV_OFFSET.If CONFIG_ENV_OFFSET is defined in partition space,the raw data may cover the env.IF CONFIG_ENV_OFFSET = 0,will it damage MBR?Should it do some protection methods?

Thank you very much
Elen.song