iommufd: Correct IOMMU_HWPT_ALLOC_NEST_PARENT description

The IOMMU_HWPT_ALLOC_NEST_PARENT flag is used to allocate a HWPT. Though
a HWPT holds a domain in the core structure, it is still quite confusing
to describe it using "domain" in the uAPI kdoc. Correct it to "HWPT".

Fixes: 4ff54216 ("iommufd: Support allocating nested parent domain")
Link: https://lore.kernel.org/r/20231017181552.12667-1-nicolinc@nvidia.comSigned-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

include/uapi/linux/iommufd.h

@@ -349,9 +349,8 @@ struct iommu_vfio_ioas {
 
 /**
  * enum iommufd_hwpt_alloc_flags - Flags for HWPT allocation
- * @IOMMU_HWPT_ALLOC_NEST_PARENT: If set, allocate a domain which can serve
- *                                as the parent domain in the nesting
- *                                configuration.
+ * @IOMMU_HWPT_ALLOC_NEST_PARENT: If set, allocate a HWPT that can serve as
+ *                                the parent HWPT in a nesting configuration.
  */
 enum iommufd_hwpt_alloc_flags {
 	IOMMU_HWPT_ALLOC_NEST_PARENT = 1 << 0,