We have $(INSTALL_LIB) which is the same as $(INSTALL_PROG) but
uses correct permissions.  Loadable objects (modules) are like
shared libraries, not like programs.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Cc: Fam Zheng <famz@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>