memory.stp: do_mmap was replaced by vm_mmap.

memory.stp: do_mmap was replaced by vm_mmap.

do_mmap was completely replaced by vm_mmap, so if either is a good match
for the vm.mmap probe alias. See kernel commits 6be5ceb and dc98250.
(Note, do_mmap2 is a special case just for powerpc.)

do_munmap was partially replaced by vm_munmap, but vm_munmap calls
though do_munmap, so for the vm.munmap probe alias do_munmap is the
best match. See kernel commits a46ef99 and 17d1587.

The same is true for do_brk and vm_brk, vm_brk calls through do_brk,
so for the vm.brk probe alias do_brk is the function to probe. See
kernel commit e4eb1ff.