accel/tcg: Simplify page_get/alloc_target_data

Since the only user, Arm MTE, always requires allocation,
merge the get and alloc functions to always produce a
non-null result.  Also assume that the user has already
checked page validity.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
3 files changed