qemuBuildDriveStr: Refactor formatting of command line for 'sd' cards

Remove all the universal code since the 'else' part formats commandline
only for the SD card based disk. Note that we can use virDiskNameToIndex
without the check as we already validate that 'disk->dst' contains a
properly formatted string in the validation code.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_command.c

@@ -1449,17 +1449,8 @@ qemuBuildDriveStr(virDomainDiskDefPtr disk,
         virBufferAddLit(&opt, "if=none");
         virBufferAsprintf(&opt, ",id=%s", drivealias);
     } else {
-        int idx = virDiskNameToIndex(disk->dst);
-
-        if (idx < 0) {
-            virReportError(VIR_ERR_INTERNAL_ERROR,
-                           _("unsupported disk type '%s'"), disk->dst);
-            return NULL;
-        }
-
-        virBufferAsprintf(&opt, "if=%s",
-                          virDomainDiskQEMUBusTypeToString(disk->bus));
-        virBufferAsprintf(&opt, ",index=%d", idx);
+        virBufferAsprintf(&opt, "if=sd,index=%d",
+                          virDiskNameToIndex(disk->dst));
     }
 
     /* werror/rerror are really frontend attributes, but older