iommu: Fix htmldocs warnings in sysfs-kernel-iommu_groups

Below warnings are fixed:

Documentation/ABI/testing/sysfs-kernel-iommu_groups:38: WARNING: Unexpected indentation.
Documentation/ABI/testing/sysfs-kernel-iommu_groups:38: WARNING: Block quote ends without a blank line; unexpected unindent.
Documentation/ABI/testing/sysfs-kernel-iommu_groups:38: WARNING: Enumerated list ends without a blank line; unexpected unindent.
Documentation/ABI/testing/sysfs-kernel-iommu_groups:38: WARNING: Unexpected indentation.
Documentation/ABI/testing/sysfs-kernel-iommu_groups:38: WARNING: Block quote ends without a blank line; unexpected unindent.

Fixes: 63a81674 ("iommu: Document usage of "/sys/kernel/iommu_groups/<grp_id>/type" file")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lore.kernel.org/linux-next/20201126174851.200e0e58@canb.auug.org.au/Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20201126090603.1511589-1-baolu.lu@linux.intel.comSigned-off-by: Will Deacon <will@kernel.org>

Documentation/ABI/testing/sysfs-kernel-iommu_groups

@@ -40,23 +40,24 @@ KernelVersion:	v5.11
 Contact:	Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
 Description:	/sys/kernel/iommu_groups/<grp_id>/type shows the type of default
 		domain in use by iommu for this group. See include/linux/iommu.h
-		for possible values. A privileged user could request kernel to
-		change the group type by writing to this file. Presently, only
-		three types of request are supported:
-		1. DMA: All the DMA transactions from the device in this group
-			are translated by the iommu.
-		2. identity: All the DMA transactions from the device in this
-			     group are *not* translated by the iommu.
-		3. auto: Change to the type the device was booted with.
-		Note:
-		-----
+		for possible read values. A privileged user could request kernel to
+		change the group type by writing to this file. Valid write values:
+
+		========  ======================================================
+		DMA       All the DMA transactions from the device in this group
+		          are translated by the iommu.
+		identity  All the DMA transactions from the device in this group
+		          are not translated by the iommu.
+		auto      Change to the type the device was booted with.
+		========  ======================================================
+
 		The default domain type of a group may be modified only when
-		1. The group has *only* one device
-		2. The device in the group is not bound to any device driver.
-		   So, the users must unbind the appropriate driver before
-		   changing the default domain type.
-		Caution:
-		--------
+
+		- The group has only one device.
+		- The device in the group is not bound to any device driver.
+		  So, the users must unbind the appropriate driver before
+		  changing the default domain type.
+
 		Unbinding a device driver will take away the driver's control
 		over the device and if done on devices that host root file
 		system could lead to catastrophic effects (the users might