ide-floppy: remove struct idefloppy_capacity_descriptor

Also,
- remove the accompanying 4 byte idefloppy_capacity_header.
- rename functions from idefloppy_... to ide_floppy_... after cleanup.
- simplify loop in ide_floppy_get_capacity() by reversing if-test condition
  logically.
- finally, fix white space and checkpatch.pl issues

Signed-off-by: Borislav Petkov <bbpetkov@yahoo.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>