linux-user: Fix h2g usage in page_find_alloc

linux-user: Fix h2g usage in page_find_alloc

Paul's comment on my first approach to fix the h2g usage in
page_find_alloc finally open my eyes about what the code is actually
supposed to do:

With the help of h2g_valid we can no cleanly check if a freshly allocate
page (for host usage) is guest-reachable and, in case it is, mark it
reserved in the guest's address range.

Signed-off-by: Jan Kiszka <[email protected]>
Signed-off-by: Kirill A. Shutemov <[email protected]>
Acked-by: Edgar E. Iglesias <[email protected]>
Signed-off-by: Aurelien Jarno <[email protected]>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5957 c046a42c-6fe2-441c-8c8c-71466251a162