s390/compat: fix mmap compat system calls

The native 31 bit and the compat behaviour for the mmap system calls differ:

In native 31 bit mode the passed in address for the mmap system call will be
unmodified passed to sys_mmap_pgoff().
In compat mode however the passed in address will be modified with
compat_ptr() which masks out the most significant bit.

The result is that in native 31 bit mode each mmap request (with MAP_FIXED)
will fail where the most significat bit is set, while in compat mode it
may succeed.

This odd behaviour was introduced with d381589 "[S390] mmap: add missing
compat_ptr conversion to both mmap compat syscalls".

To restore a consistent behaviour accross native and compat mode this
patch functionally reverts the above mentioned commit.

Cc: stable@vger.kernel.org
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/compat_linux.c

@@ -620,7 +620,6 @@ asmlinkage unsigned long old32_mmap(struct mmap_arg_struct_emu31 __user *arg)
 		return -EFAULT;
 	if (a.offset & ~PAGE_MASK)
 		return -EINVAL;
-	a.addr = (unsigned long) compat_ptr(a.addr);
 	return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
 			      a.offset >> PAGE_SHIFT);
 }
@@ -631,7 +630,6 @@ asmlinkage long sys32_mmap2(struct mmap_arg_struct_emu31 __user *arg)
 
 	if (copy_from_user(&a, arg, sizeof(a)))
 		return -EFAULT;
-	a.addr = (unsigned long) compat_ptr(a.addr);
 	return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd, a.offset);
 }