Rename __flush_tlb*() to local_flush_tlb*() as it's more appropriate, and ready
to differentiate local from global TLB flushes when SMP is introduced.

Whilst we're at it, get rid of __flush_tlb_global() and make
local_flush_tlb_page() take an mm_struct pointer rather than VMA pointer.
Signed-off-by: David Howells <dhowells@redhat.com>