mmc: core: improve reasonableness of bus width setting for HS400es

mmc_select_hs400es() calls mmc_select_bus_width() which will continue
to set 4bit transfer mode if fail to set 8bit mode. The bus width
should not be set to 4bit in HS400es.

When fail to set 8bit mode, need return error directly for HS400es.

Signed-off-by: Hongjie Fang <hongjiefang@asrmicro.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>