package/mtd: add host-acl dependency for host

package/mtd: add host-acl dependency for host

When compiling the host version of mtd, --with-jffs and --with-ubifs are
always set, meaning --with-xattr is set by default. The xattr support
only work if 'sys/acl.h' is available, otherwise the feature is silently
dropped (a warning is shown during the configuration step).

This patch adds a dependency on host-acl for host-mtd, so that the xattr
feature is correctly supported. Logic to have xattr support is already
there and working for the non-host flavour.

Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Reviewed-by: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>