KVM: PPC: Book3S HV P9: Improve exit timing accounting coverage

The C conversion caused exit timing to become a bit cramped. Expand it
to cover more of the entry and exit code.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210528090752.3542186-18-npiggin@gmail.com