powerpc/perf/hv-24x7: Dont create sysfs event files for dummy events

powerpc/perf/hv-24x7: Dont create sysfs event files for dummy events

The hv_24x7 performance monitoring unit creates a list of supported
events from the event catalog obtained via HCALL. The hv_24x7 catalog
could also contain invalid or dummy events with names like RESERVED*.
These events do not have any hardware counters backing them. Add a
check to string compare the event names to filter such events out.

Result on power9 machine:

Before this patch:
  .....
  hv_24x7/PM_XLINK2_OUT_ODD_CYC,chip=?/              [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_DATA_COUNT,chip=?/       [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_TOTAL_UTIL,chip=?/       [Kernel PMU event]
  hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT,chip=?/         [Kernel PMU event]
  hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT_MISS,chip=?/    [Kernel PMU event]
  hv_24x7/PM_XTS_ATSD_SENT,chip=?/                   [Kernel PMU event]
  hv_24x7/PM_XTS_ATSD_TLBI_RCV,chip=?/               [Kernel PMU event]
  hv_24x7/RESERVED_NEST1,chip=?/                     [Kernel PMU event]
  hv_24x7/RESERVED_NEST10,chip=?/                    [Kernel PMU event]
  hv_24x7/RESERVED_NEST11,chip=?/                    [Kernel PMU event]
  hv_24x7/RESERVED_NEST12,chip=?/                    [Kernel PMU event]
  hv_24x7/RESERVED_NEST13,chip=?/                    [Kernel PMU event]
  ......

dmesg:
  [    0.000362] printk: console [hvc0] enabled
  [    0.815452] hv-24x7: read 1530 catalog entries, created 537 event attrs (0 failures), 275 descs

After this patch:
  ......
  hv_24x7/PM_XLINK2_OUT_ODD_AVLBL_CYC,chip=?/        [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_CYC,chip=?/              [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_DATA_COUNT,chip=?/       [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_TOTAL_UTIL,chip=?/       [Kernel PMU event]
  hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT,chip=?/         [Kernel PMU event]
  hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT_MISS,chip=?/    [Kernel PMU event]
  hv_24x7/PM_XTS_ATSD_SENT,chip=?/                   [Kernel PMU event]
  hv_24x7/PM_XTS_ATSD_TLBI_RCV,chip=?/               [Kernel PMU event]
  hv_24x7/TOD,chip=?/                                [Kernel PMU event]
  ......

dmesg:
  [    0.000357] printk: console [hvc0] enabled
  [    0.808592] hv-24x7: read 1530 catalog entries, created 509 event attrs (0 failures), 275 descs

Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
[mpe: Simplify ignore_event(), minor change log formatting]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201228085204.18026-1-kjain@linux.ibm.com