package/mtd: add ubihealthd missing comment

Commit 42a3fee35e67d8d946f52a82bfa88ee6fd9f04b6 forgot to add comment on
headers 3.17+

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/mtd/Config.in

@@ -148,6 +148,9 @@ config BR2_PACKAGE_MTD_UBIHEALTHD
 	default y
 	depends on BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_17 # getrandom()
 
+comment "ubihealthd needs a toolchain w/ headers >= 3.17"
+	depends on !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_17
+
 config BR2_PACKAGE_MTD_UBIMKVOL
 	bool "ubimkvol"
 	default y