accel/tcg: Introduce probe_access_full

Add an interface to return the CPUTLBEntryFull struct
that goes with the lookup.  The result is not intended
to be valid across multiple lookups, so the user must
use the results immediately.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>