part_nr_sects_read backport wrong

The kernel patch for openVZ 6 incorrectly backported {{part_nr_sects_read}}. This symbol was added as a function (as opposed to a static inline), but not subsequently exported.

Out-of-tree modules attempting to use this symbol cannot be loaded.

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[44213954.644909] dattobd: Unknown symbol part_nr_sects_read
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