powerpc/pseries: Limit EPOW reset event warnings

Kernel prints respective warnings about various EPOW events for
user information/action after parsing EPOW interrupts. At times
below EPOW reset event warning is seen to be flooding kernel log
over a period of time.

May 25 03:46:34 alp kernel: Non critical power or cooling issue cleared
May 25 03:46:52 alp kernel: Non critical power or cooling issue cleared
May 25 03:53:48 alp kernel: Non critical power or cooling issue cleared
May 25 03:55:46 alp kernel: Non critical power or cooling issue cleared
May 25 03:56:34 alp kernel: Non critical power or cooling issue cleared
May 25 03:59:04 alp kernel: Non critical power or cooling issue cleared
May 25 04:02:01 alp kernel: Non critical power or cooling issue cleared

These EPOW reset events are spurious in nature and are triggered by
firmware without an actual EPOW event being reset. This patch avoids these
multiple EPOW reset warnings by using a counter variable. This variable
is incremented every time an EPOW event is reported. Upon receiving a EPOW
reset event the same variable is checked to filter out spurious events and
decremented accordingly.

This patch also improves log messages to better describe EPOW event being
reported. Merged adjacent log messages into single one to reduce number of
lines printed per event.

Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Vipin K Parashar <vipin@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>