dmaengine: idxd: Fix incorrect descriptions for GRPCFG register

Fix incorrect descriptions for the GRPCFG register which has three
sub-registers (GRPWQCFG, GRPENGCFG and GRPFLGCFG).
No functional changes

Signed-off-by: Guanjun <guanjun@linux.alibaba.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Acked-by: Lijun Pan <lijun.pan@intel.com>
Link: https://lore.kernel.org/r/20231211053704.2725417-3-guanjun@linux.alibaba.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/idxd/registers.h

@@ -440,12 +440,14 @@ union wqcfg {
 /*
  * This macro calculates the offset into the GRPCFG register
  * idxd - struct idxd *
- * n - wq id
- * ofs - the index of the 32b dword for the config register
+ * n - group id
+ * ofs - the index of the 64b qword for the config register
  *
- * The WQCFG register block is divided into groups per each wq. The n index
- * allows us to move to the register group that's for that particular wq.
- * Each register is 32bits. The ofs gives us the number of register to access.
+ * The GRPCFG register block is divided into three sub-registers, which
+ * are GRPWQCFG, GRPENGCFG and GRPFLGCFG. The n index allows us to move
+ * to the register block that contains the three sub-registers.
+ * Each register block is 64bits. And the ofs gives us the offset
+ * within the GRPWQCFG register to access.
  */
 #define GRPWQCFG_OFFSET(idxd_dev, n, ofs) ((idxd_dev)->grpcfg_offset +\
 					   (n) * GRPCFG_SIZE + sizeof(u64) * (ofs))