libbinder: Choose the binder driver at runtime based on system/vendor process.

This is needed since llndk libraries may cause the system variant of libbinder (and therefore
compile time checks are not enough) to be loaded in a vendor process. In that case, it should not be
initing the driver with /dev/binder. It should use /dev/vndbinder instead.

Bug: 124128212

Test: Device boots
Test: play YouTube videos, use camera to take pictures / record video (sanity) on devices supporting
      legacy vndk(sailfish) and also devices supporting current vndk.

Change-Id: Ia5581efa04c8d4adc6af39668b0aa98e84324a27
Signed-off-by: Jayant Chowdhary <jchowdhary@google.com>