Clarify naming of the mp/bmp dma buffers:

 - Rename mp to rq as it is the request buffer

 - Rename bmp to rsp as it is the response buffer

This reduces confusion about what the buffer content is based on their
name.

Link: https://lore.kernel.org/r/20220911221505.117655-9-jsmart2021@gmail.comCo-developed-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>