scsi: ufs-qcom: Name the dev_ref_clk_ctrl registers

scsi: ufs-qcom: Name the dev_ref_clk_ctrl registers

In preparation for adding another optional register range to the ufs-qcom
driver, name the existing optional register range "dev_ref_clk_ctrl_mem".
This allows the driver to refer to the optional register ranges by name
rather than index.

No device-tree files actually have to be updated due to this change, since
none of them actually declares these registers.

Link: https://lore.kernel.org/r/20200710072013.177481-3-ebiggers@kernel.org
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>