KVM: PPC: drop duplicate tracepoint

Commit 29577fc0 ("KVM: PPC: HV: Remove generic instruction emulation")
caused a build failure with allyesconfig:

arch/powerpc/kvm/kvm-pr.o:(__tracepoints+0xa8): multiple definition of `__tracepoint_kvm_ppc_instr'
arch/powerpc/kvm/kvm.o:(__tracepoints+0x1c0): first defined here

due to a duplicate definition of the tracepoint in trace.h and
trace_pr.h.  Because the tracepoint is still used by Book3S HV
code, and because the PR code does include trace.h, just remove
the duplicate definition from trace_pr.h, and export it from
kvm.o.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>