perf/dwc_pcie: Convert the events with mixed case to lowercase

Group #1 events had both upper and lower case characters in their names.
Trying to count such events with perf tool results in an error:

$ perf stat -e dwc_rootport_10008/Tx_PCIe_TLP_Data_Payload/ sleep 1
event syntax error: 'dwc_rootport_10008/Tx_PCIe_TLP_Data_Payload/'
\___ Bad event or PMU

Unable to find PMU or event on a PMU of 'dwc_rootport_10008'

event syntax error: '..port_10008/Tx_PCIe_TLP_Data_Payload/'
\___ unknown term 'Tx_PCIe_TLP_Data_Payload' for pmu 'dwc_rootport_10008'

valid terms: eventid,type,lane,config,config1,config2,config3,name,period,percore,metric-id

Run 'perf list' for a list of valid events

Usage: perf stat [<options>] [<command>]

-e, --event <event> event selector. use 'perf list' to list available events

Perf tool assumes the event names are either in lower or upper case. This
is also mentioned in
Documentation/ABI/testing/sysfs-bus-event_source-devices-events

"As performance monitoring event names are case
insensitive in the perf tool, the perf tool only looks
for lower or upper case event names in sysfs to avoid
scanning the directory. It is therefore required the
name of the event here is either lower or upper case."

Change the Group #1 events names to lower case.

Signed-off-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
Link: https://lore.kernel.org/r/20241016210136.65452-1-ilkka@os.amperecomputing.com
Signed-off-by: Will Deacon <will@kernel.org>