This allows the ibm,get-system-parameter RTAS call to succeed for the
DIAGNOSTICS_RUN_MODE system parameter.
The problem can be seen with "ppc64_cpu --run-mode" from the
powerpc-utils package which fails before this patch with "Machine does
not support diagnostic run mode".
This is corrected by using the rtas_st_buffer() function to write to
the buffer.
The RTAS constants are also moved out into a header file, some new
constants added and the surrounding code slightly simplified.
Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
[agraf: remove some commentary]
Signed-off-by: Alexander Graf <agraf@suse.de>