ppc64_cpu: Check {get,set}_attribute return values
ppc64_cpu: Check {get,set}_attribute return values

Take a look at the return value of the fprintf/scanf, and propagate
the return code. This removes a compiler warning.

Signed-off-by: Joel Stanley <4816dabf8db1bc6cac35b3a24cab2ff844b5b0c7@jms.id.au>

leitao/powerpc-ibm-utils-debian,leitao/powerpc-ibm-utils-debian,kamalesh-babulal/powerpc-utils,kamalesh-babulal/powerpc-utils,kamalesh-babulal/powerpc-utils,mdroth/powerpc-utils,mdroth/powerpc-utils,leitao/powerpc-ibm-utils-debian,shenki/powerpc-utils,mdroth/powerpc-utils,shenki/powerpc-utils,shenki/powerpc-utils