valgrind/i386: avoid false positives on KVM_SET_MSRS ioctl

struct kvm_msrs contains padding bytes. Let's use a designated
initializer on the info part to avoid false positives from
valgrind/memcheck. Do the same for generic MSRS, the TSC and
feature control.

We also need to zero out the reserved fields in the entries.
We do this in kvm_msr_entry_set as suggested by Paolo. This
avoids a big memset that a designated initializer on the
full structure would do.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
