exec: Fix prototype of phys_mem_set_alloc and related functions

exec: Fix prototype of phys_mem_set_alloc and related functions

phys_mem_alloc and its assigned values qemu_anon_ram_alloc and
legacy_s390_alloc must have identical argument lists.

legacy_s390_alloc uses the size parameter to call mmap, so size_t is
good enough for all of them.

This patch fixes compiler errors on i686 Linux hosts:

  CC    alpha-softmmu/exec.o
exec.c:752:51: error:
 initialization from incompatible pointer type [-Werror]
exec.c: In function 'qemu_ram_alloc_from_ptr':
exec.c:1139:32: error:
 comparison of distinct pointer types lacks a cast [-Werror]
exec.c: In function 'qemu_ram_remap':
exec.c:1283:21: error:
 comparison of distinct pointer types lacks a cast [-Werror]

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-id: 1380481005-32399-1-git-send-email-sw@weilnetz.de
Signed-off-by: Anthony Liguori <aliguori@amazon.com>