linux-user: Simplify target_madvise

The trivial length 0 check can be moved up, simplifying some
of the other cases.  The end < start test is handled by
guest_range_valid_untagged.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230707204054.8792-27-richard.henderson@linaro.org>
1 file changed