InputReader::getSwitchState always returns AKEY_STATE_UNKNOWN
because SwitchInputMapper::getSources() returns 0 which cannot
match any source mask including AINPUT_SOURCE_ANY. As a result
initial lid switch detection is broken.
This change adds a new source constant AINPUT_SOURCE_SWITCH
that indicates that the source has switches.
Change-Id: I5321ecf0ce84f1c2b4535f6c163d3f4dcf9b7a9b
89de57a8d2