OvmfPkg/MptScsiDxe: Report targets and one LUN

The controller supports up to 8 targets in practice (Not reported by the
controller, but based on the implementation of the virtual device),
report them in GetNextTarget and GetNextTargetLun. The firmware will
then try to communicate with them and create a block device for each one
that responds.

Support for multiple LUNs will be implemented in another series.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2390
Signed-off-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20200504210607.144434-7-nikita.leshchenko@oracle.com>

OvmfPkg/MptScsiDxe/MptScsiDxe.inf

@@ -24,8 +24,10 @@
   OvmfPkg/OvmfPkg.dec
 
 [LibraryClasses]
+  BaseMemoryLib
   DebugLib
   MemoryAllocationLib
+  PcdLib
   UefiBootServicesTableLib
   UefiDriverEntryPoint
   UefiLib
@@ -33,3 +35,6 @@
 [Protocols]
   gEfiExtScsiPassThruProtocolGuid        ## BY_START
   gEfiPciIoProtocolGuid                  ## TO_START
+
+[FixedPcd]
+  gUefiOvmfPkgTokenSpaceGuid.PcdMptScsiMaxTargetLimit   ## CONSUMES