Remove the pseries scanlog driver.

This code supports functions from Power4-era servers that are not present
on targets currently supported by arch/powerpc. System manuals from this
time have this description:

  Scan Dump data is a set of chip data that the service processor gathers
  after a system malfunction. It consists of chip scan rings, chip trace
  arrays, and Scan COM (SCOM) registers. This data is stored in the
  scan-log partition of the system’s Nonvolatile Random Access
  Memory (NVRAM).

PowerVM partition firmware development doesn't recognize the associated
function call or property, and they don't see any references to them in
their codebase. It seems to have been specific to non-virtualized pseries.

References:

Historical Linux commit from February 2003 (interesting to note this seems
to be the source of non-GPL exports for rtas_call etc):
https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=f92e361842d5251e50562b09664082dcbd0548bb

IntelliStation and pSeries docs which refer to the feature:
http://ps-2.retropc.se/basil.holloway/ALL%20PDF/380635.pdf
http://ps-2.kev009.com/rs6000/manuals/p/p615-6C3-6E3/6C3_and_6E3_Users_Guide_SA38-0629.pdfSigned-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210920173203.1800475-1-nathanl@linux.ibm.com