Let's let glibc do the right thing for dense/sparse selection.
The _alpha_iobase code has been unused since the switch to libpciaccess. It
really should have been killed by fba700f1f6.
Signed-off-by: Matt Turner <mattst88@gmail.com>
Tested-by: Michael Cree <mcree@orcon.net.nz>
Signed-off-by: Keith Packard <keithp@keithp.com>