cmd: correct ELF-related commands dependencies

Enable BOOTM_ELF by default for all configs with LIB_ELF selected.
Use OF_LIBFDT as dependency for CMD_ELF_FDT_SETUP.

Signed-off-by: Maxim Moskalets <maximmosk4@gmail.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index 0cf0d8a..5d34282 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -324,7 +324,7 @@
 config BOOTM_ELF
 	bool "Support booting ELF images"
 	depends on CMD_BOOTM && LIB_ELF
-	default n
+	default y if LIB_ELF
 	help
 	  Support booting ELF images via the bootm command.
 
@@ -500,8 +500,7 @@
 config CMD_ELF_FDT_SETUP
 	bool "Flattened Device Tree setup in bootelf cmd"
 	depends on CMD_ELF
-	select LIB_LIBFDT
-	select LMB
+	select OF_LIBFDT
 	help
 	  Do FDT setup in bootelf command optionally by param -d, which
 	  allows to bring additional system info (e.g. /memory node) to