qemu: add capabilities for the three ESP family SCSI controllers

qemu: add capabilities for the three ESP family SCSI controllers

Probing for the NCR53C90 controller is a little unusual. The
qom-list-types QMP command returns a list of all types known to
the QEMU binary. It does not distinguish devices which are user
creatable from those which are built-in.

Any QEMU target that supports PCI will have the DC390 / AM53C974
devices because they are PCI based. Due to code dependencies
in QEMU though, existence of these two devices will also pull in
the NCR53C90 device (called just 'esp' in QEMU). The NCR53C90 is
not user-creatable and can only be used when built-in to the
machine type.

This is only the case on sparc machines, and certain mips64 and
m68k machines.  IOW, we don't rely on qom-list-types as a guide
for existence of NCR53C90, as it shouldn't really exist in most
QEMU binaries.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>