mariadb: drop my-small.cnf handling

Unbreaks builds without BR2_PACKAGE_MARIADB_SERVER as this only gets
installed if the server is enabled.

As pointed out in commit 2b82e014b40 (package/mariadb: bump version to
10.3.10), this file has been removed upstream in newer versions as it hasn't
been updated in >8 years and the compiled in defaults are sensible, so
completely remove the file handling instead of adding logic to only install
it if the server is enabled.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/mariadb/mariadb.mk

@@ -112,8 +112,6 @@ endif
 # We also don't need the test suite on the target
 define MARIADB_POST_INSTALL
 	mkdir -p $(TARGET_DIR)/var/lib/mysql
-	$(INSTALL) -D -m 644 $(TARGET_DIR)/usr/share/mysql/my-small.cnf \
-		$(TARGET_DIR)/etc/mysql/my.cnf
 	$(RM) $(TARGET_DIR)/usr/bin/mysql_config
 	$(RM) -r $(TARGET_DIR)/usr/share/mysql/test
 endef