keystone2: config: update default mtd

Because it is possible for the MTD number to change, causing a
filesystem mount failure, we should use the volume name instead
of the MTD number and let Linux resolve the correct one.

Signed-off-by: Mike Scherban <m-scherban@ti.com>
diff --git a/include/configs/k2e_evm.h b/include/configs/k2e_evm.h
index d83e07e..a28ceb7 100644
--- a/include/configs/k2e_evm.h
+++ b/include/configs/k2e_evm.h
@@ -20,7 +20,7 @@
 #define CONFIG_EXTRA_ENV_KS2_BOARD_SETTINGS				\
 	"addr_mon=0x0c140000\0"						\
 	"args_ubi=setenv bootargs ${bootargs} rootfstype=ubifs "	\
-	"root=ubi0:rootfs rootflags=sync rw ubi.mtd=2,2048\0"		\
+	"root=ubi0:rootfs rootflags=sync rw ubi.mtd=ubifs,2048\0"	\
 	"name_fdt=uImage-k2e-evm.dtb\0"					\
 	"name_mon=skern-k2e-evm.bin\0"					\
 	"name_ubi=k2e-evm-ubifs.ubi\0"					\
diff --git a/include/configs/k2hk_evm.h b/include/configs/k2hk_evm.h
index ffddf13..eae7721 100644
--- a/include/configs/k2hk_evm.h
+++ b/include/configs/k2hk_evm.h
@@ -20,7 +20,7 @@
 #define CONFIG_EXTRA_ENV_KS2_BOARD_SETTINGS				\
 	"addr_mon=0x0c5f0000\0"						\
 	"args_ubi=setenv bootargs ${bootargs} rootfstype=ubifs "	\
-	"root=ubi0:rootfs rootflags=sync rw ubi.mtd=2,2048\0"		\
+	"root=ubi0:rootfs rootflags=sync rw ubi.mtd=ubifs,2048\0"	\
 	"name_fdt=uImage-k2hk-evm.dtb\0"				\
 	"name_mon=skern-k2hk-evm.bin\0"					\
 	"name_ubi=k2hk-evm-ubifs.ubi\0"					\
diff --git a/include/configs/k2l_evm.h b/include/configs/k2l_evm.h
index 805164a..57da057 100644
--- a/include/configs/k2l_evm.h
+++ b/include/configs/k2l_evm.h
@@ -20,7 +20,7 @@
 #define CONFIG_EXTRA_ENV_KS2_BOARD_SETTINGS				\
 	"addr_mon=0x0c140000\0"						\
 	"args_ubi=setenv bootargs ${bootargs} rootfstype=ubifs "	\
-	"root=ubi0:rootfs rootflags=sync rw ubi.mtd=2,4096\0"		\
+	"root=ubi0:rootfs rootflags=sync rw ubi.mtd=ubifs,4096\0"	\
 	"name_fdt=uImage-k2l-evm.dtb\0"					\
 	"name_mon=skern-k2l-evm.bin\0"					\
 	"name_ubi=k2l-evm-ubifs.ubi\0"					\