[PATCH] SHPC: Fix SHPC Contoller SERR-INT Register bits access

Current SHPCHP driver doesn't take care of RsvdP/RsvdZ[*] bits in
controller SERR-INT register. This might cause unpredicable
results. This patch fixes this bug.

[*] RsvdP and RsvdZ are defined in SHPC spec as follows:

    RsvdP - Reserved and Preserved. Register bits of this type are
    reserved for future use as R/W bits. The value read is
    undefined. Writes are ignored. Software must follow These rules
    when accessing RsvdP bits:

	- Software must ignore RsvdP bits when testing values read
          from these registers.
	- Software must not depend on RsvdP bit's ability to retain
          information when written
	- Software must always write back the value read in the RsvdP
	  bits when writing one of these registers.

    RsvdZ - Reserved and Zero. Register bits of this type are reserved
    for future use as R/WC bits. The value read is undefined. Writes
    are ignored. Software must follow these rules when accessing RsvdZ
    bits:

        - Software must ignore RsvdZ bits when testing values read
	  from these registers.
	- Software must not depends on a RsvdZ bit's ability to retain
	  information when written.
	- Software must always write 0 to RsvdZ bits when writing one
	  of these register.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Cc: Kristen Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>