[U-Boot] Multiple stdin/out without CONFIG_CONSOLE_MUX?

[Stephen Warren]

Mathieu, John,

While looking into a CONFIG_CONSOLE_MUX-related issue, I noticed the
following:

include/configs/u8500_href.h:136:	"stdin=serial,usbtty\0"
include/configs/u8500_href.h:135:	"stdout=serial,usbtty\0"
include/configs/snowball.h:180:	"stdout=serial,usbtty\0"

Those all include multiple devices in the stdin/stdout definitions.
However, those config files don't set CONFIG_CONSOLE_MUX. I assume this
causes usbtty to be ignored, and only serial used?

Or perhaps U-Boot even fails to parse the variable at all, since
CONFIG_SYS_CONSOLE_IS_IN_ENV isn't set on those boards? Actually, there
are a few more boards with that problem:

> include/configs/km/keymile-common.h:258:	"stdout=serial\0"						\
> include/configs/MVBC_P.h:146:	"stdout=serial\0"					\
> include/configs/MVBLM7.h:460:	"stdout=serial\0"					\
> include/configs/MVSMR.h:129:	"stdout=serial\0"					\
> include/configs/sandbox.h:91:					"stdout=serial\0" \
> include/configs/snowball.h:180:	"stdout=serial,usbtty\0"					\
> include/configs/u8500_href.h:135:	"stdout=serial,usbtty\0"					\