package/mtd: drop unrecognized option

install-tests option has been removed since version 2.1.3 and
http://git.infradead.org/mtd-utils.git/commitdiff/7170a28d46d5db1e7a9da24a5555a194a233ef0b

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/mtd/mtd.mk

@@ -47,9 +47,9 @@ MTD_CONF_OPTS += --disable-ubihealthd
 endif
 
 ifeq ($(BR2_PACKAGE_MTD_TESTS),y)
-MTD_CONF_OPTS += --enable-tests --enable-install-tests
+MTD_CONF_OPTS += --enable-tests
 else
-MTD_CONF_OPTS += --disable-tests --disable-install-tests
+MTD_CONF_OPTS += --disable-tests
 endif
 
 # If extended attributes are required, the acl package must