OPP: debugfs: Use performance level if available to distinguish between rates

OPP: debugfs: Use performance level if available to distinguish between rates

Some OPP tables have entries with same rate and different performance
level. For these entries, using only the rate as the debugfs directory name
causes below error:

debugfs: 'opp:5000000' already exists in 'soc@0-1c00000.pci'

Fix it by appending the performance level to the dir name if available.

Reported-by: Bjorn Andersson <andersson@kernel.org>
Closes: https://lore.kernel.org/linux-arm-msm/75lzykd37zdvrks5i2bb4zb2yzjtm25kv3hegmikndkbr772mz@w2ykff3ny45u/
Fixes: 05db35963eef ("OPP: Add support to find OPP for a set of keys")
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>