env: ubi: KConfig: add CONFIG_ENV_UBI_VOLUME_REDUND

Introduce the KConfig option CONFIG_ENV_UBI_VOLUME_REDUND for defining
the name of the UBI volume used to store the redundant environment.

Signed-off-by: Markus Klotzbuecher <markus.klotzbuecher@kistler.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Cc: Kyungmin Park <kmpark@infradead.org>

hs: get rid of stm32mp1* build errors
diff --git a/env/Kconfig b/env/Kconfig
index b943917..b8bdfb0 100644
--- a/env/Kconfig
+++ b/env/Kconfig
@@ -507,6 +507,12 @@
 	help
 	  Name of the volume that you want to store the environment in.
 
+config ENV_UBI_VOLUME_REDUND
+	string "UBI redundant volume name"
+	depends on ENV_IS_IN_UBI
+	help
+	  Name of the redundant volume that you want to store the environment in.
+
 endif
 
 config USE_DEFAULT_ENV_FILE