Re-use the TARGET_PAGE_BITS_VARY mechanism to define
TARGET_PAGE_SIZE and friends when not compiling per-target.
Inline qemu_target_page_{size,mask,bits} as they are now trivial.
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>