linux-user: Use "!= 0" when checking if MAP_FIXED_NOREPLACE is non-zero

linux-user: Use "!= 0" when checking if MAP_FIXED_NOREPLACE is non-zero

In pgd_find_hole_fallback(), Coverity doesn't like the use
of "if (MAP_FIXED_NOREPLACE || ...)" because it's using a
logical operator on a constant other than 0 or 1 and its
heuristic thinks we might have intended a bitwise operator
instead.

The logic is correct (we are checking whether the host really
has a MAP_FIXED_NOREPLACE or whether we fell back to the
"#define as 0 to ignore" from osdep.h); make Coverity
happier by explicitly writing out the comparison with zero.

Fixes: Coverity CID 1431059
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20201103142636.21125-1-peter.maydell@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>