android: correcly set LOCAL_EXPORT_C_INCLUDE_DIRS

 - Don't add ${hw}/${hw}, but ${hw} to the includes path. The former
does not exist.
 - Set the variable for libkms.

Inspired by the work of from Chih-Wei from the Android-x86 project.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>