Fix for Calc page scaling - see #i54993#

If a print range's manual breaks forced it over more pages than specified
by the sheet scale settings, the zoom calculation wasn't able to
converge on a zoom level, so it bottomed out at ZOOM_MIN.

This issue only appears if the Calc/Print/Page/ForceBreaks option is
selected and simply ensures the minimum number of pages is at least
the number required by the breaks in the sheet.

Change-Id: Iba36e850081718b1aa43e5c3db3c883530885853
Reviewed-on: https://gerrit.libreoffice.org/6532
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>