powerpc/hv-24x7: Add rtas call in hv-24x7 driver to get processor details

For hv_24x7 socket/chip level events, specific chip-id to which
the data requested should be added as part of pmu events.
But number of chips/socket in the system details are not exposed.

Patch implements read_24x7_sys_info() to get system parameter values
like number of sockets, cores per chip and chips per socket. Rtas_call
with token "PROCESSOR_MODULE_INFO" is used to get these values.

Subsequent patch exports these values via sysfs.

Patch also make these parameters default to 1.

Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200525104308.9814-3-kjain@linux.ibm.com

arch/powerpc/include/asm/rtas.h

@@ -483,5 +483,11 @@ static inline void rtas_initialize(void) { };
 
 extern int call_rtas(const char *, int, int, unsigned long *, ...);
 
+#ifdef CONFIG_HV_PERF_CTRS
+void read_24x7_sys_info(void);
+#else
+static inline void read_24x7_sys_info(void) { }
+#endif
+
 #endif /* __KERNEL__ */
 #endif /* _POWERPC_RTAS_H */