MPIIX has only single channel IDE which can be configured for either primary or
secondary legacy I/O ports and IRQ.  So, get rid of the unneeded second probe
entry in mpiix_init_one() and of the invalid (but unused anyway) enable bits in
mpiix_pre_reset().

Warning: this cleanup has only been compile-tested...
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>