scripts/kvm/kvm_stat: Cleanup of TracepointProvider

scripts/kvm/kvm_stat: Cleanup of TracepointProvider

Variables with bad names like f and m were renamed to their full name,
so it is clearer which data they contain.

Unneeded variables were removed and the field generating code was
moved in an own function.

dict.iteritems() was removed as directly iterating over a dictionary
also yields the needed keys.

Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Message-Id: <1452525484-32309-20-git-send-email-frankja@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>