lib: Kconfig dependencies for pseudo-random library

drivers/rng/sandbox_rng.c requires rand() to be defined but configuration
option CONFIG_CONFIG_LIB_RAND selected in drivers/rng/Kconfig does not
exist.

test/lib/test_aes.c requires rand() to be defined.

Fix the selection criteria for choice "Pseudo-random library support type".

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig
index 35a3bd1..893b89d 100644
--- a/drivers/rng/Kconfig
+++ b/drivers/rng/Kconfig
@@ -9,7 +9,6 @@
 config RNG_SANDBOX
 	bool "Sandbox random number generator"
 	depends on SANDBOX && DM_RNG
-	select CONFIG_LIB_RAND
 	help
 	  Enable random number generator for sandbox. This is an
 	  emulation of a rng device.
diff --git a/lib/Kconfig b/lib/Kconfig
index d040a87..ab6aff7 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -150,7 +150,8 @@
 
 choice
 	prompt "Pseudo-random library support type"
-	depends on NET_RANDOM_ETHADDR || RANDOM_UUID || CMD_UUID
+	depends on NET_RANDOM_ETHADDR || RANDOM_UUID || CMD_UUID || \
+		   RNG_SANDBOX || UT_LIB && AES
 	default LIB_RAND
 	help
 	  Select the library to provide pseudo-random number generator