Use the vma iterator API for the brk() system call.  This will provide
type safety at compile time.

Link: https://lkml.kernel.org/r/20230120162650.984577-9-Liam.Howlett@oracle.comSigned-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>