configs: support null block device and scsi debug

These are required for blktests, and currently we only support on debug
kernel for test only.
Signed-off-by: NJoseph Qi <joseph.qi@linux.alibaba.com>

config-4.19.y-x86_64-debug

@@ -1616,7 +1616,9 @@ CONFIG_PNP=y
 #
 CONFIG_PNPACPI=y
 CONFIG_BLK_DEV=y
-# CONFIG_BLK_DEV_NULL_BLK is not set
+CONFIG_BLK_DEV_NULL_BLK=m
+CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION=y
+CONFIG_CDROM=m
 # CONFIG_BLK_DEV_PCIESSD_MTIP32XX is not set
 CONFIG_ZRAM=m
 CONFIG_ZRAM_WRITEBACK=y
@@ -1753,7 +1755,8 @@ CONFIG_SCSI_DMA=y
 CONFIG_BLK_DEV_SD=y
 # CONFIG_CHR_DEV_ST is not set
 # CONFIG_CHR_DEV_OSST is not set
-# CONFIG_BLK_DEV_SR is not set
+CONFIG_BLK_DEV_SR=m
+# CONFIG_BLK_DEV_SR_VENDOR is not set
 CONFIG_CHR_DEV_SG=y
 # CONFIG_CHR_DEV_SCH is not set
 CONFIG_SCSI_CONSTANTS=y
@@ -1814,7 +1817,7 @@ CONFIG_ISCSI_BOOT_SYSFS=m
 # CONFIG_SCSI_DC395x is not set
 # CONFIG_SCSI_AM53C974 is not set
 # CONFIG_SCSI_WD719X is not set
-# CONFIG_SCSI_DEBUG is not set
+CONFIG_SCSI_DEBUG=m
 # CONFIG_SCSI_PMCRAID is not set
 # CONFIG_SCSI_PM8001 is not set
 CONFIG_SCSI_VIRTIO=y