Fix doc warnings

hardware/libhardware/include was being included with -isystem, which
hides warnings.  Fix use of doxygen function comments on on function
pointers, which are not considered functions or methods.

Bug: 32018017
Test: m -j
Change-Id: I71a1d33a9ae90b646bf22f32e052bbe22e8aca76
1 file changed