uprobes: Don't use loff_t for the valid virtual address

loff_t looks confusing when it is used for the virtual address.
Change map_info and install_breakpoint/remove_breakpoint paths
to use "unsigned long".

The patch doesn't change vma_address(), it can't return "long"
because it is used to verify the mapping. But probably this
needs some cleanups too.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Anton Arapov <anton@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154355.GA9622@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>