This fixes several problems with the lparcfg code.  In case
someone gets a sense of deja-vu, part of this was submitted last Sep, I
thought the changes went in, but either got backed out, or just got
lost.

First, change the local_buffer declaration to be unsigned char *.  We
had a bad-math problem in a 2.4 tree which was built with a
"-fsigned-char" parm.  I dont believe we ever build with that parm
now-a-days, but to be safe, I'd prefer the declaration be explicit.

Second, fix a bad math calculation for splpar_strlen.

Third, on the rtas_call for get-system-parameter, pass in
RTAS_DATA_BUF_SIZE for the rtas_data_buf size, instead of letting random
data determine the size.   Until recently, we've had a sufficiently
large 'random data' value get passed in, so the function just happens to
have worked OK.   Now it's getting passed a '0', which causes the
rtas_call to return success, but no data shows up in the buffer.
(oops!).   This was found by the LTC test org.

This is in a branch of code that only gets run on SPLPAR systems.
Tested on power5 Lpar.
Signed-off-by: Will Schmidt <willschm@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>