km/common: drop unneeded std* environment variables

These variables are only used if CONFIG_SYS_CONSOLE_IS_IN_ENV
is set. This isn't the case, so we can drop them safely.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
cc: Valentin Longchamp <valentin.longchamp@keymile.com>
cc: Prafulla Wadaskar <prafulla@marvell.com>

include/configs/km/keymile-common.h

@@ -253,9 +253,6 @@
 	"load=tftpboot ${load_addr_r} ${u-boot}\0"			\
 	"mtdids=" MTDIDS_DEFAULT "\0"					\
 	"mtdparts=" MTDPARTS_DEFAULT "\0"				\
-	"stderr=serial\0"						\
-	"stdin=serial\0"						\
-	"stdout=serial\0"						\
 	""
 #endif /* CONFIG_KM_DEF_ENV */