tools: Remove xc_map_foreign_batch

tools: Remove xc_map_foreign_batch

It can trivially be replaced by xc_map_foreign_pages which is the
interface I want to move to going forward (by standardising on _bulk
but handling err=NULL as _pages does).

The callers of _batch are checking a mixture of a NULL return or
looking to see if the top nibble of the (usually sole) mfn they pass
has been modified to be non-zero to detect errors. _pages never
modifies the mfn it was given (it's const) and returns NULL on
failure, so adjust the error handling where necessary. Some callers
use a copy of the mfn array, for reuse on failure with _batch, which
is no longer necessary as _pages doesn't modify the array, however I
haven't cleaned that up here.

This reduces the twist maze of xc_map_foreign_* by one, which will be
useful when trying to come up with an underlying stable interface.

NetBSD and Solaris implemented xc_map_foreign_bulk in terms of
xc_map_foreign_batch via a compat layer, so xc_map_foreign_batch
becomes an internal osdep for them.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>
Cc: George Dunlap <george.dunlap@eu.citrix.com>