powerpc/perf: Define perf_event_print_debug() to print PMU register values

Currently the sysrq ShowRegs command does not print any PMU registers as
we have an empty definition for perf_event_print_debug(). This patch
defines perf_event_print_debug() to print various PMU registers.

Example output:

CPU: 0 PMU registers, ppmu = POWER7 n_counters = 6
PMC1:  00000000 PMC2: 00000000 PMC3: 00000000 PMC4: 00000000
PMC5:  00000000 PMC6: 00000000 PMC7: deadbeef PMC8: deadbeef
MMCR0: 0000000080000000 MMCR1: 0000000000000000 MMCRA: 0f00000001000000
SIAR:  0000000000000000 SDAR:  0000000000000000 SIER:  0000000000000000

Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
[mpe: Fix 32 bit build and rework formatting for compactness]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/include/asm/perf_event_server.h b/arch/powerpc/include/asm/perf_event_server.h
index 3fd2f1b6..9ed73714 100644
--- a/arch/powerpc/include/asm/perf_event_server.h
+++ b/arch/powerpc/include/asm/perf_event_server.h
@@ -14,6 +14,7 @@
 #include <linux/device.h>
 #include <uapi/asm/perf_event.h>
 
+/* Update perf_event_print_debug() if this changes */
 #define MAX_HWEVENTS		8
 #define MAX_EVENT_ALTERNATIVES	8
 #define MAX_LIMITED_HWCOUNTERS	2