linux-user: Fix types in uaccess.c

linux-user: Fix types in uaccess.c

For copy_*_user, only 0 and -TARGET_EFAULT are returned; no need
to involve abi_long.  Use size_t for lengths.  Use bool for the
lock_user copy argument.  Use ssize_t for target_strlen, because
we can't overflow the host memory space.

Reviewed-by: Peter Maydell <[email protected]>
Signed-off-by: Richard Henderson <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Message-id: 20210212184902.1251044[email protected]
[PMM: moved fix for ifdef error to previous commit]
Signed-off-by: Peter Maydell <[email protected]>