ltp: add dependency libaio

ltp: add dependency libaio

When libaio has been populated to sysroot, ltp will be compiled with
libaio. If rpm/deb package of libaio doesn't be created, bitbake
core-image-xxx will fail with:

| Processing task-core-apps-console...
| Processing ltp...
| error: Failed dependencies:
| 	libaio.so.1(LIBAIO_0.4) is needed by ltp-20120614-r0.i586
| 	libaio.so.1(LIBAIO_0.1) is needed by ltp-20120614-r0.i586
| 	libaio.so.1 is needed by ltp-20120614-r0.i586
| ERROR: Function failed: do_rootfs

Add libaio to ltp dependency to fix this issue.

Similiar to [Yocto #2973]

(From OE-Core rev: 4945eafb7dd0d9e59760fdfad98982937be27517)

Signed-off-by: Kang Kai <kai.kang@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>