Remove LOCAL_COPY_HEADERS

Copying headers is bad for enforcing build dependencies because it puts
the headers in a location that anyone can include them without depending
on the module.  The new build system will not support copying headers.

Remove LOCAL_COPY_HEADERS, they are already available through
LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)

Change-Id: I545228718b7a3ad108f155673df8e7faf1c6dd3e