target/hppa: Use PRIV_P_TO_MMU_IDX in helper_probe

Direct privilege level to mmu_idx mapping has been
false for some time.  Provide the correct value to
hppa_get_physical_address.

Fixes: fa824d99f9b ("target/hppa: Switch to use MMU indices 11-15")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
1 file changed