watchdog: sp5100_tco: Remove code that may cause a boot failure

A problem was found on PC's with the SB700 chipset: The PC fails to
load BIOS after running the 3.8.x kernel until the power is completely
cut off. It occurs in all 3.8.x versions and the mainline version as of
2/4. The issue does not occur with the 3.7.x builds.

There are two methods for accessing the watchdog registers.

 1. Re-programming a resource address obtained by allocate_resource()
to chipset.
 2. Use the direct memory-mapped IO access.

The method 1 can be used by all the chipsets (SP5100, SB7x0, SB8x0 or
later). However, experience shows that only PC with the SB8x0 (or
later) chipsets can use the method 2.

This patch removes the method 1, because the critical problem was found.
That's why the watchdog timer was able to be used on SP5100 and SB7x0
chipsets until now.

Link: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1116835
Link: https://lkml.org/lkml/2013/2/14/271

Signed-off-by: Takahisa Tanaka <mc74hc00@gmail.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Cc: stable <stable@vger.kernel.org>