net: openthread: enable NEWLIB_LIBC_NANO only if NEWLIB_LIBC

Without this change, NEWLIB_LIBC_NANO gets selected even
when building OpenThread application with PICOLIBC.

Signed-off-by: Damian Krolik <[email protected]>

Author: Damian-Nordic

subsys/net/openthread/Kconfig.defconfig

@@ -35,7 +35,7 @@ choice LIBC_IMPLEMENTATION
 endchoice
 
 config NEWLIB_LIBC_NANO
-	default y
+	default y if NEWLIB_LIBC
 
 config NUM_METAIRQ_PRIORITIES
 	default 1