Update note about libelf support.

elfutils on android-4.4 (AOSP, and Omni so far) is 0.138.

A few symbols ktap depends on are in 0.148.

If elfutils is updated to 0.148 or newer the cflags to disable libelf
can be removed and Add a line:

LOCAL_STATIC_LIBRARIES := libelf

Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>